Tactics 101 (not supposed to but probably will contain spoilers)

kamuizin

1° of all: you need a thief capable of dual class, doesn't matter which class.

raise set snare to 50% at least, use all your snares to prepare for a fight. When you finsh of use all of them, go to your thief character menu, press dual class, choose any other class and it's done, do not confirm the dual class, after choose any class just cancel the dual and all your snares will be renewed to be used.

It's a bug, so use it based in your sense of roleplay at your risk.