You could try baiting the trap at the very back instead of on the trigger. If they are licking the peanut butter off of the trigger it may not be enough pressure to set it off. They may be setting it off as they leave by fussing with a peanut butter sticky mouth. If they have to go to the back of the cage to get the bait, they will have to actually step on the trigger. I'm also asuming this is a one sided trap. I only have experience with those. If it's 2 sided, try smearing cheerios in peanut butter (tiny bitof PB, for the sent) and stringing through yarn to tie to the trigger. They will have to fuss with it then. I hope this is helpful. Good luck.