I couldn't find this reported already, but I've found that items can get "stuck" in the inventory. This seems to occur when swapping items around rapidly, seemingly when switching items into or out of a chest as well as the creative menu. When this occurs, the item will be unable to be moved at all, including being unable to be dropped, and will visually glitch out in a jittery sort of way.
Thank you for your report!
We're tracking this issue in MCPE-65815, so this ticket is being resolved and linked as a duplicate.
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