For me, I have a bug where sometimes while on fast forward, sometimes hits won't register. This is also only with high bullet speed (both with and without orbital flame. I (and this is an educated guess) think that this is framerate problem, and might be able to be solved by maybe extending the hitbox from the previous frame to the current frame, so on higher fps the hitbox will be normal, but on lower fps the hitbox will be longer to accommodate for the lost frames. Please don't take my word for all this, this could 100% be the stupidest thing I've ever said.
What you guessed isn’t properly wrong, it is mainly due to the time given to process hitboxes. I think I know exactly why this is happening since I’ve only changed one thing in the enemies from v1.1.1 to v1.1.2 and that was removing rigidbodies. Once I deploy the next version I make sure that it doesn’t happen