Tuner Bushings Always Popping Up

Any one else have this problem. I have had a few higher-end Epiphone G-400s in the past (A G-400 Standard and a G-400 1966 Limited Edition Reissue)both had Grover tuners. Very nice guitars. My only problem is that the tuner bushing always kept popping up, leaving the washer to rattle any time you moved the guitar. I know that it only takes a few turns with a 3/8 wrench to snuggle em' back down, but it can be a hassle when it happens at a friends house or other place.