I had a problem like that on my wife�s mto3. Bearings went put new ones in then within a week gone again, what I found was the shop we bought the bike from had over tightened the nut and squished the inner spacer buy about 2mm. So when the wheel was done up the inner part of the bearing was being pushed in by about 1 or 2mm does not sound much but when riding the force on the inner part of the bearing made them eat themselves. So we got a new inner spacer then never had a problem again .Just a thought if the shop over tightened the wheel