I've tried many things such as editing configs, removing mods, and changing gamerules, but issue still persists. The problem is that, complicated blocks render slowly and half the time not at all, and most of the time the inventory (and jei) will not render, and rarely render very slowly. there should be no issue with rendering as I'm using 16g RAM MC. Also the issue disappears when I remove quark. Here's my game log

Closing because I'm cleaning up the issues page. This issue is really old and probably irrelevant. If you feel i should be re-opened please tell me why.