I have the Inception upgrade and some time when you insert 3 backpacks into {The backpack} the last one gets deleted but not every time and this just started happening out of the blue.

Have a backpack with the Inception Upgrade and place a backpack in it is the only way I have reproduced it.

I'm using the Direwolf20 1.20 pack for this with some mods added but none of them change inventory that I know of.

Backpack getting voided in backpack!

Forge: 47.1.76
Soph. BP: 3.18.59.909

Void upgrade -_- I think I reported about something like this in the past too, and it was the same thing my bad.