Cannot sell items when full

When i'm full (i've got 6 items) i'm unable to sell one item to get another. When i sell one the fps drop, the item sells, wait 1 second and then the item reappears in my item box. Doesn't matter how fast i react, i'm unable to sell one and buy another i'll be willing to make a video of it if this is not a known bug ps: i had some pretty high fps drops last game (before maintenance) when in late game. I had a static 10 (no swain)