I have found some difficulties wtih full packs and overflow windows. The specific example I can think of was this.

In team mission. Fighting BOSS. Item was picked up by leader before boss fight. Overflow window appears with token and reward. Durring battle with Boss I click on token and reward in overflow window after making room in my pack. I get error message at bottom of screen You can not do this right now (refering to the fact that I am in a fight). After fight is over the overflow window is empty, my pack is empty. Zoneing does not refresh the pack or overflow. I even close the overflow and combine a inplant/cluster (to force the overflow to reopen) and there is nothing in there. The items were lost.