About two months ago, both my rear turn signals fell off my 2017 VX300 (9500 miles, mostly pavement). Two day ago, my left front turn signal fell off.
The turn signals are supported in the bodywork by expanding the rubber at the base of the stalk with what Kawasaki calls a washer and nut. The washer/nut expand the rubber portion so that it cannot pass through the mounting hole. The tension on the wiring harness is what holds the turn signal assembly in place.
Apparently the vibration of the bike causes the bodywork to wear on the rubber ultimately causing it to fail. Repair consists of replacing the entire turn signal assembly (about $50+ USD each).
Anyone else had this issue? Interestingly enough, I also have a V650 (2014 model) that uses the same system that has had no problems. Did Kawasaki get some different materials?