I recently rescued the wereraven, but I can't leave the castle. The door I came from is sealed shut, and there are no buttons I can find to open it. No walkthroughs tells of any ways to leave. I have cleared the whole castle except for Strahd himself and a weird room I can't enter du to turning traps and a teleporter.

Does anyone know how to leave?

Got a map picture of where you are?

Edit; If you're in the main hall, you should be able to just walk in front of the door leading to outside, and it should open. Just tested it.

The map is from online.

I'm trying to access the area called "To/From Old Svalich Road North". I'm stuck in the main hall outside of that room. The door to the entrance/exit is sealed, and I don't know how to open it again.

That's very odd. As I mentioned, that door should just open as you walk in front of it.
Does it help changing to stepping mode or vice versa? (Left-click the compass)

I tried stepping mode too now, but no change. :/

It's like it could only be opened from the other side when I entered, but it won't let me go back and leave. There's a similar door across the hall, and that one is opened with a button on either side. But this door don't have one at this side.

I'm getting the feeling the game somehow thinks you're visiting the castle for the first time; hazarding a guess the door would not open for you, since you're forced to meet Strahd the first time you enter the castle.

So yeah, I think you hit a bug then.

Maybe running into and out of the dinner room where you met Strahd the first time would reactivate the door? I really don't have an idea.

If all else fails, there might be a hacky way to get out of there; in the game Menzoberranzan it was possible to shuffle level .DAT files around, making you warp to an entirely different map. I managed to go from the city of Menzoberranzan back to the surface. Trying this path might be a bit of a headache though.
If you have a save from before you enter the castle, maybe just try going inside, see if the door functions normally, and then rescue the raven.

I have been suspecting a bug too, and it makes a lot of sense that the game would think I'm there for the first time. I've seen a lot of map-resetting. It doesn't affect quests etc, but it respawns everything everywhere, makes the are undiscovered on my map, respawns items, and closes doors. It haven't been game breaking until now, because other doors can simply be unlocked with the keys I've collected.

How can I edit the .DAT file? Do I need a special program, or any special instructions I need to follow?

Sounds like the game folder is partially read-only or something? Is that possible?

I'm not sure how I did the DAT file thing; been a while. You don't edit them directly, but you rename them.

They're basically data for every map that you've been in. There's a WORK folder in the game folder, where the game temporarily stores maps as long as the game's running and you have a save loaded.
Every file name in here corresponds with a certain map. For example, say LEV001.DAT is the starting area, and you could travel to LEV002.DAT, Svalich Road... Let's say LEV003.DAT would be Barovia. You could rename LEV003.DAT to LEV002.DAT, so you can instantly travel to Barovia from the starting area.

I have no idea which LEVel number corresponds to which map.

There might be a huge downside to this though. You might end up in an illegal part of the map when traveling this way.
I can't remember if this is the case.

I still think it's best if you figure out why the game isn't saving data. Enemies should stay dead, and flags should stay, well, flagged. You might run into even more problems later down the line.

Hmm, I did some puzzling and I think I might be able to help you out.

After testing I found that LEV012.DAT is the main floor of Strahd's castle. I've zipped up my LEV012.DAT from one of my later savegames. If you overwrite your LEV012.DAT from your savegame with mine and then load your save, you'll basically have my map as I explored and flagged it, and thus with a functioning door.
Keep in mind the items you left behind on this floor will likely be gone, replaced with whatever I left behind (and backup your save, just in case).

Edit: Link removed.

Thank you! :D

You really when out of your way to help me. I will try to see if I manage to fix this. So I guess I'll just replace the files in the correct folders then? I will let you know how it worked out.

It kind of worked, but I had to do some extra work. It turned out LEVEL12.DAT was missing. Adding it wasn't enough. So I went to another floor of the castle, saved the game there. Reloaded. No difference. Then I imported LEVEL12.DAT to an empty save. Reloaded my saved game, and THEN reloaded the empty save file. This updated the LEVEL12.DAT file, and I'm now escaping the castle.

So thank you for saving me from castle Ravenloft. I owe you a feather now. <3

Glad to hear you can continue! Cheers.