Sorry for the delay, I haven’t been entirely on top of my forum notifications lately. First of all, you need to understand that Pencil2D doesn’t really have an dedicated internal player at all. There’s just the canvas that you use for editing and then the playback is sort of tacked on to it. So when you play your animation in Pencil2D, no files are generated, all it does is to automatically increase the current frame counter by one, wait for 1/fps seconds, repeat until the end of the playback range is reached and occasionally skip a frame if the playback falls behind. Some parts of the program like onion skins behave differently when playback is active, but again, nothing is being generated specifically for playback, it’s just slight differences in behaviour.
Accordingly, when you export your animation to a GIF or MP4 file, that file is generated not from some intermediate playback files (because there are none) but directly from the original frame data.
I’m glad you were able to find a workaround for the debris issue, but I’d still appreciate if you could describe that issue in more detail so we can fix it properly. Saving and reopening the project should not be necessary. This goes for the crash mentioned in your original post as well. A crash is a pretty severe issue, and I’d be grateful if you could share the exact steps that lead to it as well as your Pencil2D version and operating system so we can properly fix it.