I haven't tested it with smaller backpacks, but with backpack size set to 7 rows, when a player dies the dropped backpack is 6x6. Whatever was in row 7 is lost if there was no empty space in the first 6 rows for the plugin to move the contents of row 7 there. Tested it with unique and unstackable items to be sure. After emptying the contents of the 6 visible rows the backpack doesn't disappear.

I see, thanks for reporting that.

Confirmed fixed on version 3.0.1. Thanks a lot!