Try this: If one of the gear gets stuck, enter Chaos mode and press + or - to change the gear, then leave Chaos mode.
I had this problem too. And I spent 3 hours looking for a solution. Still, my last save was 6 hours ago. Oh and there is another way to enter Chaos mode: Caps Lock + Middle Mouse Button. It's only mentioned in the game once, and nowhere else.
Beautiful work, this fix is wonderful =3
I couldn't equip the Crossblade and it was stuck on the EarthCaller, so I entered Chaos Form, switched to EarthCaller, and presto, now Normal Form can freely switch gear again ^w^