Next time you have the to replace the belt I would make sure that the cam gears are torqued down to spec. If that is good and you still have some wobbling I would take them off and see if anything might have gotten stuck behind there for some reason and isn't seating properly. If none of this works and you have change the tensioner already I'm pretty much out of ideas. One last question though, are you using cheap belts or quality ones? Also, do you have the right tension on the belt?