If a shulker box loot chest is broken in a way that doesn't involve direct player interaction (eg. blowing it up), the produced item will cause a crash if any item in the inventory is picked up or if the shulker itself is hovered over if quark is installed with its shulker support on. From testing I found if broken this way when you hover over the shulker box without quark it displays a list of the shulkers contents with the first item being "????????" however when it is placed and opened it's contents will be entirely different from that list (basically causing a similar but less-worse problem). This leads me to believe that this is due to the way that vanilla Minecraft handles loot-tables, the game gets confused when said loot is generated in a shulker, as the contents of the shulker has not yet been decided yet even though it is in your inventory however when you hover over it or pick up a different inventory item with quark, it tries to access the shulker item to modify/view its contents, which have not been defined, causing a crash.

While I understand this error isn't to do with this mod itself and rather the way that Minecraft handles loot tables, I thought it would be good for you to know.

Thanks for letting me know, there's a few places I have TNT near a shulker in the structure so I could see this issue coming up fairly often.

I bet the loot tables use the location of the box to determine the seed used to randomly generate the loot, and it's generating the loot only when opened and not blown up. I was thinking that may have been a conscious decision because generating loot can cause a lot of lag, but I'm pretty sure regular chests generate and drop their loot when blown up. I'll look into it once I get some time!