Kveiuorna

Well, it seems that sp614x (the OptiFine creator) discovered what was causing the issue. He explained what it was in his Discord server, so I simply took a screenshot of it. I'm not certain if I can link an invite to the Discord here. Although, here's what he said: https://i.imgur.com/9a9l1yo.png

Sorry if this is spam at this point, but I'd like to comment again and show that it still exists in the full 1.13.2 release, this time even without the aforementioned particle command:

This is at a generic enderman farm that worked fine prior to 1.13+ versions.

Just want to mention that this issue persists in 1.13.2-pre2. Command used was /particle minecraft:firework ~ ~10 ~ 1 1 1 1 10000

I'd like to just comment, and say that it even affects complete overkill hardware in 1.13.1. I've attached an image above, showing the issue with an i7-7700k and a GTX 1080 Ti displayed in the F3 screen. Sorry if this comment is unneeded. I just figured someone may have come to the false conclusion that since the original reporter has low-end hardware, that may have been a factor.