I bought a MT300 about a year ago. Also a new 5" backing plate. Light to moderate use. Only my cars and occasionally a friends. All is good right? Well to day I fired it up. Was doing some correction with microfiber 5" pad and about 5 minutes in the backing plate falls off. I look and the threads on the backing plate post are gone. I'm like hmmm. Weird. Put another backing plate on. 5 minutes later, same thing. Threads are gone . Two backing plates in 10 minutes and in the last year no issues. Any ideas?? I used the supplied wrench to tighten but why no issues before now? Now i need 2 new backing plates

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