My 396T and 396XT had to have the screw tightened every time they were put on the belt clip. My 436's clip "button" has never budged even with daily, constant use.
For those who are trotting out the same old BS about quality and "$600 scanner", I have maintained a fleet of Motorola Minitor II pagers for nearly 20 years, with some of them being dropped 3 stories, accidentally flushed in a toilet (don't ask), and run over by vehicles, with little if any damage. Even those devices still had belt clip failures, and they were made when Motorola made things to be damn near indestructible. Get used to belt clip failures - they're a fact of life.