im playing in a minecraft server in fabric, and i xray the chests, and sometimes it detects it, but sometimes it doesnt detects it until i open the chest, same with lots of blocks, sorry if im being lazy, if you are interested i can provide instructions to replicate the bug

Sorry, missed this somehow.
Open F3 debug screen, check BlockFinder row on the left-bottom.
It shows how many chunks are loaded and visible by cheatutils.
If it says 0, there is some mod conflict

no same problem for me too now that I saw this even though it says there's 441 chunks loaded even when running blocks.restartBlockFinder() the only thing I saw that looks REMOTLY right (1.20.4 fabric)