I don't really think reducing the amount of XP would solve this problem. These kind of situations happen to me all the time, but as you said, friends are bribing each other. Police officers are already limited with the amount of bribes they can do in a certain amount of time.
I think there was a topic about the part of reducing their job rank XP, but I guess that doesn't really matter since you can compensate with a few arrests your XP loss, where just one arrest gives you 10 XP already (2 XP cuffing + 8 XP arresting).
Just ignore the situation, since after a minute you're going after an another wanted player.
