[CLIENT] , Skins unequipping or default skins automatically being equipped.
So when you go to teambuilder, and it automatically re-assigns your champ you last played most of the times you will get a bug where it will show both of the skins being equipped (I added a picture of how this looks). This is, from my observations, the only thing that is abnormal whenever this happens to me. However I constantly have my skins unequipped in other game modes as well.
How you can normally reproduce this is to go back to the teambuilder lobby or most lobbies after a game and check the skin tab. If you don't unequip and make sure the skin is re-equipped it doesn't put your skin on. Even after I do this sometimes it still unequips my skins. It is a fairly frequent bug that occurs on a daily basis for me. There is nothing more aggravating then spending money on a skin and forcibly not being able to use it...