I've got a full inventory, holding a few (less than a stack) lapislazuli.
I tried to stock up my inventory by taking lapislazuli out a chest - and held long, to get all.
Result: My Inventory is stocked up to 1 stack of lapislazuli, the chest is empty.
The surplus lapislazuli are lost (forever?)
Expected result: Drop surplus items on floor or leave them in chest.
Same happened with iron ingots, pretty sure it "works" the same way with every item
Thank you for your report! This issue was, however, reported at an earlier time as MCPE-9960. Please add a comment summarizing your experience there.