Mongtec’s Taiwan Service Center repairs and maintains WTO driven tool holders and angle heads. You do not have to send the unit back to the original manufacturer, and you do not have to be in Taiwan — units are accepted from anywhere in the world. Mongtec Precision is a Taiwanese brand, designed and engineered in Taichung, Taiwan.
Send photographs of the unit and the WTO model number. That is usually enough for a first opinion on whether it is worth repairing, and it costs nothing. Only then does it make sense to pay for freight.
Bearing replacement, spindle and shaft regrinding, seal and coolant-path renewal, gear inspection and replacement, runout correction, and a final re-inspection against specification. The unit comes back with its inspection record. Nothing is machined or replaced before the quote is accepted.
If the wear has gone too far, Mongtec will say so rather than quote a rebuild that will not hold. In that case a Mongtec unit on the same open turret or spindle interface is the alternative — nothing changes on the machine side.