I started a vanilla world in 1.18.2 and played a short session. Then I put some items in chests, closed the game, and installed a few mods including Quark. (I wasn't concerned with world gen changes.)

Upon reopening the world my chests were replaced with quark:variant_chest and they lost all nbt, including the inventories.

I recommend not replacing chests unless they have no NBT set. (No LootTable or inventory.) Or at least make sure that the NBT is preserved.

Minecraft version 1.18.2
Quark version 3.2-358
Forge version 40.1.70

latest.log

Quark doesn't do this. I'm not sure why it would happen but I can guarantee there's no code in quark to replace blocks in the world already.