It happened with some red rreign items a few times before. I wanted to move the single item into my holiday galery but after clicking "move into shop" and "Holiday and Events" it is still in my inventory. When I try it a second time it is gone. But I can not say right now, if it went two times into my galery or just one time and I just had to make a second try. I have so many double items of them in there, that I have to try out again and control the amount of the items before sending.

Update: I tried out two times more, while controlling the amount of items in my gallery before sending. But this time it did not happen once more. The problem seems to be gone for now.