O.K., maybe I'm doing something wrong. Maybe I'm stupid. Maybe I'm very stupid. But I just can't seem to know what to do in those situations where a group of enemies are hiding behind locked doors and won't come out no matter what. Does that really make that sector entirely unwinnable until I can get a good lockpicker? There really must be some way to headbutt the freaking door into submission, must there not? I imagine those stupid grunts in there, twiddling their thumbs, laughing at my pathetic attempts to blow their brains off their heads while complimenting each other on how gorgeous their stupid red shirts look. Really, is there not anything I can do? I don't mind the answer being just some incredibly stupid oversight on my part, as long as I can get some progress.

a) Grenades on wooden doors (majority).
b) Explosives on all doors.

c) Get a good lockpick and save yourself the hassle. There are quite a few of them.

I also seem to recall the possibility of using a crowbar on padlock doors (?). Can't remember for sure.

d) shoot the lock
e) find the right key
f) come back (much) later and find that the dudes are now in a different part of the map

Seems like a decent amount of options to me. :)

I played the game more than a dozen times and I still learn something new. Interesting...

a) Grenades on wooden doors (majority).

Not carrying any at the moment. It still feels like a waste to me, specially in this specific sector where there are two buildings (with two doors each, to add insult to injury), but I'll bear that in mind (I didn't want to try it when I was carrying grenades because I was not sure if it would work (and yeah, I'm ironmanning it, any form of loading a previous save is off-limits)).

b) Explosives on all doors.

Yeah, I did try that one once. Good times. Shame explosives are so hard to come by (so far, at least).

c) Get a good lockpick and save yourself the hassle. There are quite a few of them.

Yep, that's the obvious solution to try when I get a decent one. Which brings me to my next question: does trying again after failing have any effect at all on my chances? Is it worth valuable time and APs, or am I likely to just fail every single time if I failed on my first twenty-something attempts? ¬¬ Do crowbars work at all in vanilla JA1 (for doors, I mean)? I think I remember having read they do work in some later games.

d) shoot the lock

Tried that one. Several times. Am I supposed to get any indication that it's working (other than the door opening, which didn't happen)? It might be likely for Juan to miss the lock five times in a row from point blank, but perhaps I was just not doing it right? You sure this works in vanilla JA1?

e) find the right key

Well, I was actually carrying two different keys at the time, but couldn't open any of the four doors in the sector. Also, since the keys were grouped, am I supposed to separate them so I can try them both individually, or would the game automatically pick the right key from a stack?

f) come back (much) later and find that the dudes are now in a different part of the map

With my luck, I'm sure if I skip that sector, they'll launch an attack from there while I'm elsewhere and reconquer all of the island. But yeah, I'll bear it in mind.

Well, still not the "easy" solution I was hoping for, but I guess all is not lost. I still think there should be a way to bring those buggers out. They're supposed to be defending the sector, for Pete's sake! I could just bar the doors and windows and call the sector mine for all they care. I even tossed a grenade in from a window and they'd just stay there, making faint and definite sounds from every direction. Man, this game sure is tough for a first-timer, specially one with the hubris to ironman it on the first playthrough. Anyway, thanks for the help, guys.

Picking locks is the easiest solution most of the time. But you need a merc with medium/high mechanical skill, otherwise it'll fail pretty often. Other than that, shooting the lock or using granades is the next step.

I wouldn't use explosives (dynamite, C4) for doors. If you really have no other choice, you might as well blow up the wall in a more convenient spot. Try with a shotgun at point blank, or an assault rifle; revolvers are just not very good for that. It'll take a few attempts but it works with weak doors. The right key is picked automatically. Each key is tied to a specific lock, even if they stack that doesn't mean they're the same. Sometimes you'll find one hidden in the furniture, sometimes they're carried by guards in another sector. You really should be guarding your borders with militia anyway. But losing a sector is usually not a problem, unless it contains important resources (facilities, trees). And even then, reconquering one is easier than assaulting it for the first time. Yeah, unfortunately, enemies camping the same spot forever is a recurring problem of the whole series, not just JA1. It's very annoying, but thankfully doesn't happen too often.

You could always leave the sector and re-enter it right away, enemies will be relocated at random places on the map (that also means they can be put inside the house again however), and unfortunately, you will have to re-explore the sector from scratch.

Also, lockpicking isn't luck related. The strength on locks range from 0 to 100. 0 being a door that isn't locked, and 100 being a door that is extremely difficult to pick. When a mercenary attempts to pick a lock, the game take the mercenary's mechanic, wisdom and dexterity skills, throw them into a formula, and ends up with a number ranging from 0 to 100+, the game then substract a percentage penalty if the merc is tired, or if the locksmith kit is in less than perfect (100%) condition. Then, if the mercenary's lockpicking score is higher than the lock strength, the door will unlock. You can retry in case your first attempt at lockpicking was made when your merc was tired, or in case your locksmith kit was in less than perfect condition (you can combine multiple locksmith kits to keep them in perfect conditions, simply put a kit in your merc's left hand, then select a second kit and click on the gray item slot underneath the first locksmith kit to combine them) but otherwise attempting to pick a lock several times will not give different results.

Mercs with high health can pry open weak locks with a crowbar, the formula to pry open a lock is: (Health / 4) + (Health / 8) - Fatigue. Hurl, with his whooping 100 in Health, is the best dude to pry crates and locks open (up to 37 in lock strength). And, although I know a lot of people use and suggest to use Ice as a field mechanic early in the game, but the truth is, with his excellent health, Ice is more effective at picking locks with a crowbar than he is with a locksmith kit.

Weak sauce locks can be blown open by rifles and sufficiently powerful handguns. Anything beyond that will require explosives: Grenade for medium strength locks and bombs for high strength locks. But if you consider blowing up a door with a bomb, I advise you blow up the wall right next to the door (up, down, left or right, not diagonal) instead, that way you will not only blow the door open but you will also puncture a hole in the wall, giving you a bigger hole in the wall to shoot the bad guys inside or storm in the building. Also remember that C4 and TNT can blow holes into walls but Eagle Fearballs do not, so if all you have on your merc is an Eagle Fearball or enough material to craft one, and you intend to blow a door open with it, put it directly on the door to maximize your chance of blowing it open, don't put it on the wall.

Personally, until you can afford Magic or a merc with an equal or superior score in lockpicking, I highly advise you to carry a couple of grenade and a bundle of TNT with you at all time just in case you face a door you can't open, or just in case you face a situation where those would be handy (which happens more often than you might think.)

Also, lockpicking pro-tips:
If there are still hostiles on the map, always equip your locksmith with the best armor you have, don't be afraid to pack an Ultra Shield in addition to your treated Kevlar helmet and your treated Spectra Shield, because picking a lock open is an excellent way to get shot at point blank range by the welcoming committee, and good locksmith are hard to come by. If you worry about the lack of pockets on an Ultra Shield and worry about your ammo carrying capacity, have your locksmith carry a gun that packs more than six rounds and have him tag along with the guy that carries the wall probe and give that guy an extra round of ammo to reload the locksmith's pistol or rifle.

Also, give rocks to the guy that carries the wall probe. Rocks are good at creating distractions, when a rock lands on the ground, it create noise, and enemies will often come and investigate that noise. If you throw a couple rocks in front of a door, there is a small chance an enemy will pop outside to investigate. And even if they don't come outside to investigate, there is a high chance that they will spend their entire turn turning and walking around the room, trying to find where that noise came from, wasting precious action points in the process, meaning when you open the door, there's a good chance the enemy will not have enough action points to interrupt your turn and shoot your locksmith.

And when in doubt, just use a bomb.

Thanks, that's some useful info blueskirt.