Well, thanks for all your input! For me, resetting the rotation via .setAngularVelocity was enough, becauce my ship would explode on collisions, anyway. I just needed a lose safety backup for that it doesn’t rotate the wrong way for some other spooky reason than collisions.
Anyway, i sticked to using JBullet because i already put a lot of work in my implementation, but i also looked into dyn4j (2D physics) when @pspeed pointed it out. It seems to do a great job even in jme. So for future 2D-gameplay-projects, i think i would build onto that!