It seems that since the patch yesterday, it is no longer possible to move stacks of items in storage from one spot to another. Instead you have to move them one at a time. I tried it in account, character and premium storage and it was the same thing. I don't have quantities of anything in the IM storage so I couldn't test that.
In the ss I was trying to move that all 8 of the dance scrolls but as you can see, only one was moved. Not a biggie in this case but that's going to be a problem when you want to relocate a stack of 999 lol