I remember losing my wits due to all of the bugs in this game, especially the ones causing CTD mid-mission. One solution I found ages ago helped a lot and made the game playable with almost no CTDs during missions. I'll paste the original post and link here so you can try the fix yourselves. This should be pretty easy to implement as a patch if GOG's willing and if it's not done yet. I own a non-gog version of this game so I'm not sure whether this issue is already addressed or not, someone with the game (and the files required) should confirm this.

All credits to the people who originally found this solution, I make no claim none whatsoever.

*sic*

*** SOLUTION TO THE CULTIST BUG ***

After examining the WeapDef.dat file under the Data folder I've found out how to solve the infamous cultist bug.

YOU NEED TO START A NEW GAME FOR THE CHANGES TO TAKE EFFECT

(or it may be enough to save again, but I haven't tested)

1. Open WeapDef.dat in the Data folder under the Chaos Gate folder.

2. Find the section containing the Laspistol.

3. Change "PlazPistHit.wav" to "PlazpistHit.wav" (note the lower case 'p').

4. Save.

5. Start a new game.

Enjoy your cultists without CTD.

*/sic*

EDIT: NOTE TO MODS/ADMINS - Please, for the love of anything you hold dear, let the post editor notify me if I don't have enough rep to post a link. I cannot express how f*cking frustrating it is to search for a solution for not being able to post here for some reason.

Thanks mate. Nice post.