"Cannot resist the constant urge to steal objects."
This ailment may cause a character to randomly steal items from your inventory, and it may trigger an encounter while resting out in the open. In this encounter the klepto will have stolen a possession from another party member and it will lead to them getting into an argument. You will have to choose who to side with, and the character you didn't side with will become angry with you or storm off and leave the party.
But on the other hand, kleptomania is useful ailment when you take a 'Steal idol' quest. If you rest this village and leave, and your klepto randomly said that he/she stole the idol. This encounter you can impound the idol from klepto, just consider his/her loyalty.