My experience has been that the menu/app organizing stuff has always been flaky, and I haven't figured out if selecting/dragging things in a particular way leads to more or less success. I usually just keep fiddling with the dragging until something (finally) works... sounds silly... but maybe I'm just agreeing... yeah, it does suck, common issue, etc...

I'm running the 51.3 update, but I don't remember things being any more reliable in 50.2 or the stock install before any updates.