1) Trying to dig a dummy out of a hole, only to get repeatedly stuck on one niggling little bit of dirt that I can barely see and that my diggerbeam refuses to hit.
Yeah they get stuck on everything. Just tap your jetpack like crazy (this makes the jetpack work better for some reason, probably a bug) and they'll work their way through it usually.
2) Robots (Robot 1 specifically) tumbling out of control and rocketing into the ground because I had the audacity to try to correct my flight path.
Yeah, tapping the down key while jetpacking is very likely to send you spinning into the ground. Stick to tapping the jetpack key for course corrections.
3) Not so much the physics itself, but a giant problem for me; the delivery rocket can be "controlled" like other bodies, which means if I try to change bodies while a delivery is in process (and God forbid off-screen) I'll suddenly find myself in control of a flying refrigerator. Yes, selecting away from the rocket does put it back under AI control, but the AI pilot is already trippin' on LSD and that split-second of confusion can send it into a death spiral.
If you hold Q/E instead of tapping it, you can move the cursor to the body you want to control, instead of cycling through them. But yeah, the rocket AI is unbelievably bad. Dropships are much safer, but if you do find yourself in control of a rocket, just tap the up button like crazy with occasional taps on A and D to keep it pointing up.
I don't know why people in here are telling you that CC's controls don't totally suck, because they do. The radial menu is a fucking nuisance (shifts around depending on what you're using) and you can't even map the controls to keyboard, crawling basically only works on flat floors. Also the AI sucks in general. Also none of these problems will ever be fixed because the developer is a lazy twitter addict. But it's still a fun game if you can get used to it.