After a bit more digging, looks like I've answered my own question. I still haven't found the bad connection, but I should the next time it happens.
Here's the path.
That circuit in the WFCO box first feeds the outlet for the frig inside its outside access panel. Then two lines come out of that single outlet. One feeds the GFCI outlet in the bath which further feeds the kit and outside outlets as GFCI slaves.
The other line leaving the frig outlet feeds the bedroom outlets. That's the line that has to have a bad connection somewhere. Most likely, it's the frig outlet itself where two romex cables are connected to one set of outgoing contacts.
I can say this sort of wiring definitely wouldn't pass residential code. Three romex cables connected to a single outlet ouside the frig and not even in a box! To make matters worse, it isn't GFCI protected at that point!