A bit basic I know but have you checked the power adapter is plugged in properly at both ends and the integrity of the cable
Do you have a new master socket 5c MK4 where the front clips on and no screws. If so there are posts where it did not clip on correctly and was slightly loose which caused drops in connection
Looking good after the factory reset, I'll grep the logs for disconnections in a bit, but today will be my acid-test - lots of meetings.
I do have a 5cMk4, it didn't seem loose, but I popped it off and on again just to be sure.
After doing a broadband test the system wanted to book an engineer for me - is this normal practice or does it indicate something may be amiss?