SME-10 worn motor bearing on top

Hi all,
does anyone have an idea, why the top motor bearing on a SME 10 tt would be worn, such that the motor when running makes a noticeable 'peck, peck, peck' kind of noise?

Note: Proper maintenance, a drop of oil over ~ a year was done.

Over some period of time I back-tracked the odd noise back to the motor bearing, now having a play of ~ 0.1mm (maybe more). Is this some freak occurrence or can I expect a re-occurrence after some more time having a new motor put in?
This tt has quite some belt tension if e.g. compared to some other tt running a belt on the platter rim, rather than a sub-platter as is the case with the SME.

NOTE: SME has had no quarrel at all, to replace the motor at minimal cost, even though the deck is no more under any warranty.
PS: the 'odd' noise seems to come about by the bearing play allowing the armature's pole-pieces touching the stator, as the noises frequency is corresponding to the running speed i.e. 33, 45, 78 rpm.
Let me give some update on this item,

as it so happened, the motor developed (if it was not a faulty set-up in the first place?) too much up/down play. This is adjustable from the bottom of the motor by a pointed cap-screw and counter nut.

My explanation:
If that longitudinal play is too much ~ 2.5mm, the axle of the motor starts to add an up/down movement to the normal turning action. This becomes something like a 'reaming action' and would therby increase wear, by some unexpected margin.
Since the motor is in a fixed position the pull of the belt concentrates on one point only of the shaft's bearing. It will therefore wear even quicker. My suggestion would be for owners to do themselves a favour and by simply lifting the platter, check how much up/down play the unit has. If more than 0.1 - 0.2 mm it might just be a good idea to correct it before the same happens as I experienced. I do NOT have the spec. of this play, but I do have a factory new motor and the play I mentioned derives from that.