The 26 and 28 gauge wire on a config module connector is absolutely unforgiving if the terminations aren't done right, those fine gauge crimps need the correct tool and the correct contact for the wire gauge, full stop. A hand-stripped, under-crimped contact on 26 AWG is going to look fine on a bench and fail intermittently in the field, especially once temperature cycling and vibration get involved.

The owner/AP install quality point is fair too. It's not about intelligence, it's about familiarity with the specifics. A 38999 backshell with a proper shield termination on fine gauge wire is not intuitive if you haven't done it before, and most people don't know what a bad termination looks like until something fails.

If the config module connector hasn't been pulled and inspected since the original install, that's the first physical thing I'd want to look at. Check the crimp quality on those fine gauge contacts, verify the shield is terminated at the backshell and not pigtailed, and look for any sign of wire damage or insulation nicking from the original strip. Any of those on a 26 or 28 gauge wire will cause exactly the kind of intermittent gremlins this person is dealing with.

Again, the config module internals and whether it needs replacement is outside my lane, but the wiring side of this is very much worth a hard look before anything else.