The blinky light on Mary’s bike became intermittent and, after a week or two, I figured out why:
The white plastic case has a thin section labeled PUSH over the switch. After five years of exposure to the sun (it faces upward on her bike) and upwards of 2000 pushes (5 years x 200 rides/year x 2 pushes/ride), the edges of that little plate cracked, it slipped inward, and jammed the switch button.
I swapped it for the one on my bike, which mounts with the switch downward and has seen much less use since I began running the Fly 6 rear camera + blinky light, and it was all good.
The fractured plate slid snugly back in place, a few drops of IPS 3 solvent-bonded the broken edges, and a snippet of good 3M electrical tape inside the case should provide a bit of reinforcement:
It’s now on my bike, just in case it’s needed.
That was easy …