While clearing some overhanging brush along the rail trail, I probably wedged a branch between the LC40 flashlight and the fairing:
Aaaand twisted it enough to fracture the mount:
A closer look shows the infill just ripped apart:
I can’t be sure that’s what happened, because the mount actually failed several miles later, after I hit one of the potholes along Raymond Avenue. Fortunately, I saw it swinging away from the fairing, hanging by its last few threads, and managed to grab it before it vanished.
I set Slic3r for 30% infill on the replacement, but the running light been riding my fairing for three years and seems strong enough under normal use.