Minis hijacking Roamio channels for long periods

I have a Roamio Pro (series 5, software version 20.5.9) and three Minis set up with moca. No problems for many months, except... Several times a week, at all hours, the minis will hijack the Roamio, all at the same time, and I get a "currently in use by another box" message for 3 channels. This goes on for hours. What is happening and how do I stop it, or at least shorten it or make it happen in the middle of the night? Thanks.

Sorry if this has been asked, I searched but didn't find anything on point.