The game crashes in Mission 5 of the Mercenary expansion pack.

The crash happens whenever I hit the large white door that appears after I configure the crystals to blow up the ceiling.

The crash is consistent and happens every time.

Please help resolve.

Never heard of this bug myself. You're using the GOG version I take it?
Try using the small black door next to the large door.

Happens to me as well, but it's not because I'm interacting with the door. Both times I was just looking towards the doors, the small black one was open, and that's all. Well, the turret right behind it had aggroed. When I just flew quickly past, it didn't crash, at least not instantly.

Playing GOG version Win 10 64-bit.

I did a play through until this area and also experienced a crash. It seems to happen after the turrets have agroed. The key is to get past this section without triggering agro. Don't use afterburner, stay out of sight and if you get attacked by patrols draw the robots into another room before taking them out. And don't use flares ANYWHERE because they trigger agro also. IF the turrets agro, the crash will happen.

It felt like it was maybe just the one turret or the turrets in that particular area cause I was fighting a lot of the others later on. And also for me they were shooting at me for a while each time before the crash. My diagnosis is "one of these things". I guess I should report it as well.

It's the custom swatters (the turrets with homing/vulcan combo). I remember back in early 2000's when working with D3 mods I encountered this crash also. There is no fix or patch for it.

Also another way to crash the game (sometimes) if you fire at the locked door several times (just after you blast into the facility). This is caused by a particle bug in the engine.

I wish that they would release the source code as it is without the promised cleanup and update that may take until the end of time.