[Konstantinos]

Are you sure that AJailTimer[playerid] stored the timer ID? You attempt to kill the timer and that's correct but it's like it failed to do so.

Is it like?

pawn Код:

// let's say "targetid" stores the id we want to jail in the /jail or /ajail command:
AJailTimer[targetid] = SetTimerEx( ... );

Make sure you didn't write playerid by accident etc..