[FWB]

as a general rule i have found most.....not all....products we buy as consumers are made in less than high quality environments. we take for granted when there are threads in a product that they are correct, more often than not they are not manufactured correctly. to the average person they seem to be fine but after tightening and loosening a screw the threads are gone.......why?....sometimes oversized holes being used to thread....which you then loose a percentage of thread engagement, or dull tooling causing bad thread geometry. the quality and size of the fastener used can booger threads real quick.
look at the set screws closely are the threads nice? does the allen broached hole look a little funky?
if you answered yes then maybe its crappy fasteners causing it....