THIS IS A MISUNDERSTANDING, NOT ACTUAL BUG

Multiplayer server. I was in the nether, and was filling my inventory with shulker boxes full of sand and gunpowder

I tranferred shulkers full of sand from a double chest 4 columns on the left side of my inventory, then went to a different double chest 5 blocks away from the sand double chest and transferred 5 columns of gunpowder shulker boxes on the right.

At this state my inventory still correctly displayed the boxes.

When I started to place the boxes on a wall for easy conversion into TNT, the boxes placed on the wall were all sand - then I checked my inventory and EVERYTHING turned into shulkers full of sand.

Unfortunately I had turned off my video capture software, but I will try to recreate the bug to capture video.