When utilizing the jewelcrafting from Shen, if you go to the remove gems screen, then choose a different tab (combine, socket, train) without having removed a gem, and then return to the remove gem screen (again, without having originally removed a gem) you either must remove the gem from your helmet (cannot choose anything else) or close the menu and open it back up to choose a different piece of gear to remove gems from.
I have included the bug (inability to choose which piece to remove gems from) as well as the workaround (exit the menu and reenter)… Its a QOL issue but honestly at this point in development most things are QOL.