Using level sync while desynthing an item traps you in a "handling items" state.

[KageTokage]

Frequency: Guranteed, assuming steps are followed.
World name: Cactaur
Character name: Ilyana Neriskal

Steps:
1. Start desynthesizing any item while standing near a FATE that's low level enough to require level sync.
2. Hit level sync before the desynth finishes and shows you the results.
3. The game will now think that you're still desynthing an item until you log out (Not even this will work unless you close the game from outside of its interface using the X button on game's window outside of full-screen, alt+F4, or by right-clicking it on the task bar) or change zones, meaning you literally can't anything other then move around until you do, as all of your actions will be greyed out and give you the "Can't do that while handling items" message.

It's pretty hard for this to happen accidentally, but the effects are troublesome to warrant fixing it regardless. I have a suspicion that doing this with any kind of action that puts you into a "handling items" state such as dyeing or applying glamours might also be capable of causing this to happen.

[Rufalus]

Nice catch, there used to be a similar bug with repairing items during an instance that required force shutting down the game to be able to use any actions again but they fixed that one.