Here’s some esoteric silliness that may help another down the line:
Update:
Did all the cache clearing possible, no joy… but!
Forgot to say that the error was appearing identically on two virtually identical android 6 devices (running OS-exclude app 2.22.21) AND android 7 emulator Bluestacks (app latest production.)
Last night I opened Bluestacks and the error was gone. Exited. Opened the two android devices… also gone. !
A backend hiccup, maybe… :shrug: 
or, possibly related, maybe even a combo-cause…
Before entering Bluestacks, I had attempted android device Playback access of the SD on the problem cam and found it would repeatedly (though not without exception) crash the app.
Tried reformatting the SD from within the app, it reported success, exited/restarted app and checked SD capacity, had NOT reformatted, checked Playback, footage still there, still intermittent crashing.
So for sure I’m going to climb up and pull that cam, climb down and exercise the SD card in slot, power plug too, reformat card in PC, maybe, etc.