Thanks for the comment! The jerkiness is most probably shader compilation. I'm showing them to the camera before the start of the game, so theoretically they should be precompiled. I'll look for another way. The slo-mo is optional and can be switched off in gameplay options. I'll check what's the problem with crashing, it hasn't happened for a long time while testing...
I've just crashed a few times in that area and nothing happened. Will do some more testing tomorrow. Maybe there is some other factor. I'm also on Win 10. The baddies have a move chance and check against it every couple of frames. So sometimes they may just be unlucky. Also they don't move in some very narrow areas, as they would just spin in place, making it look strange. Or some of them may just be buggy :) But not everything moved in the original as well, so I guess it's acceptable.
If you are bothered by that narrow piece, try another random seed and you will get a different layout of river and enemies. I wonder if it will crash in every instance of narrow piece of river?