Have had a similar failure problem on one of 2 mounted.....in my situation, tracked it back to a slight imperfection in plastic case....used a jewelers tool and scraped a small bit of case away...solved that problem for me.....however had a different, much more major, problem with both lights.....water intrusion (1 month of use)...sanded contacts, replaced rusting batteries.....took a bit of clear tape and covered joints.....needed a magnifying glass to do this...(I get stubborn "occasionally")....no issues in last 2 months.