I can only do one string substitution batch rename and then it stops working

I've been having this issue for a while - I will select a bunch of images that are similar, then ask Bridge to rename, for example "IMG" to "Cityscape". This will work once or twice and then it won't work again until I restart Bridge. At this point, 'quit' doesn't usually work either and I have to force-quit. I'll do this over and over again, renaming one set, force-quitting, restarting bridge, doing another set, etc, but it's pretty time-consuming so I'd love to figure out how to get rid of this behaviour.

I've tried resetting the preferences/deleting cache and it's still doing the same thing.

thanks for any help.