I am also having the same issue as bigexlolith. When I attempt to activate the Atilla engine, there is no thrust, no effect, and if I press "switch propellant" my game crashes. This is pretty much a show-stopper for my playthrough if mid-end game engines won't work (especially since I play 2.5x scale JNSQ). On a clean save it seems to work, but I do not want to make a clean save and call it a day for two reasons.
1: Who wants to lose their progress?
2: If I can't solve this for good, I'm fairly certain the bug will just come back and ruin another game of mine.
I'm reaching the end of my patience. I've tried to comb through my crash log to find out why this is happening, but it's no help because the logs for this game are borderline gibberish. I tried following a general troubleshooting guide on this website, but was unable to get to the bottom of this.
We really need help with this. I have my crash log (but I don't know how to share it on here). I'm glad I'm not alone in dealing with this....but please help me.