The title says it all, and here's a picture of the "block bug"

Please open one ticket per actionable issue.

For the crash, please include the crash report as well as the latest.log file from right after the crash (before restarting MC).

For the jukebox, please describe in more detail how you're expecting it to behave and how it actually behaves. The jokebox stopping when you enter the pause menu doesn't sound wrong it me given the game is paused at that point.

The "blocks" bug aren't actually blocks, those are the break particles. If you unpause the replay, they will quickly decay. Their presence may have multiple causes. Assuming you jumped to that part of the replay either from the beginning where the blocks still existed or backwards in time (which simply restarts the replay, i.e. also jumps from the beginning), then that's because the game isn't being fully simulated while jumping, cause that would make jumping way slower than it already is. There is #311 to eventually fix that for most short-lived animations.