so the issue is when you put items into the vault with a terminal mod such as integrated dynamics I haven't tested with another method to insert but, it seems that there is a chance that when you unload the chunks or quit the world, that the items in the vault that you just put into the vault will disappear. also worth noting that I could not get that result if the whole item vault multi-block was in the same chunk. however, It was fairly consistent while the item vault on the border of 4 chunks.

In this video, you can see that I have a certain amount of items in the vault, and then when quit and reload I am missing some of said items

here is the setup the one on the left I could not get to delete any items but the one on the right is the one shown in the video witch will delete items as shown

I hope this helps I tried to collect as much info as I could I saw someone else post about this issue but they didn't narrow much down. so I am replicating it pretty consistently still not sure what the exact trigger is but I can only get it to happen on chunk borders. This is in 1.19 and its a Bug

I was able to reproduce in 1.20.1 using Create for Fabric: Fabricators-of-Create#1471

Workaround: Make sure that for every vault not on a contraption, all blocks making up the vault are in the same chunk.