Win10 SW2016 SP4 - I have working assembly mates that fail almost every time I change configurations, suppress or unsuppress other mates, or modify another mate. Then, if I change things back to where they were before the mate failure, the mate(s) that worked before now fails. To fix this I can modify the mate, delete a face from the mate selections list, re-select the exact same face I deleted, and the mate works. This fixes the mate temporarily (including the other following mates) but then they fail again soon after. This seems to indicate that the reference to a particular surface face (there are many different faces) gets lost.
I would also add that both assemblies and parts have hundreds of configurations controlled by design tables. Unfortunately, I cannot post any files because of the proprietary design. Any ideas what is going on or a workaround?