Good catch with the sound. The physics thing is caused by the game looking at all the forces impacting the player jet when checking when calculating the counteracting upwards force while tunnelling. I'll rework that. I'll check again if boss engines are immune to kill shot. There is also a bug where the boss spawns too close to an floating island which can immediately destroy one engine. (The boss spawn might still get reworked a bit with you actually seeing it jumping in.) Sorry if I'm not posting rapid fixes right now, I'm kind of in the middle of making content for 0.74 (X-Ray) but I might be able to fit in a bug-fix update before in. Please rest assured that a lot of stuff is happening though. :)
