The repair department of our sister company has had several Metabo WEPA 14-125 angle grinders come in with the same issue. The arbor lock won’t engage and it creates quite a pain come time to change your wheels. We’ve come across units in the past with a defective locking mechanism where the actual metal lock post contacts the backside of the bevel gear. Usually this happens from semi engagement of the lock while the wheel is still turning. This causes the gear to lose it’s sharp edge of the detent hole which makes the detent post not hold securely.
But these recent units we have received into our repair department were suffering from a different issue. Basically it boils down to material packing up under the plastic arbor lock button making it not depress far enough to engage fully into the bevel gear. Our video shows you where to and hot to quickly clean your grinder to get it back running again.