In case it helps anyone I’m just replacing bearings in the same motor on my sons TRS 20 and the Doga part no of the 48v 1350w motor is 32190235009.
i think the main issue is crap bearings and seal. I’ve just ordered a decent 19x12x3mm seal and SKF rubber sealed bearings (6001Z which is 12mm inner, 28mm outer and 8mm wide) from simply bearings which will hopefully be much better.