On a new May 2018 build, after 210 rounds down range the rear slide plate slipped down out of position enough to keep the slide from returning to battery. Happened two more times roughly after 40-50 rounds. With a push from my thumb, the slide returned to full battery and fire on the next pull. Anybody else had this wonderful experience? Sig wants the pistol back to examine, the CS rep told me "there are no known issues with the 365".

Yours is the first I've heard of that happening, so I'd hazard a guess that it's not a common issue. That plate shouldn't move unless there's something wrong with the retaining ledge on the striker.

Must have a piece of debris keeping it from locking in place I have two of them and no issues. Have you taken it apart and cleaned the area?

Yes, took it apart and gave her a good cleaning. I get back to the range next week and see if it solves the issue. Thanks.