On the bottom of the brake release, under the side panel, is an air valve made by Nason
NASON : Custom Engineered Switches . I was able to partly disassemble where the lever goes into the valve and clean it. Since I've cleaned it, it is happening less frequently. I haven't been motivated enough to change out the valve and I don't know if Nason will sell it directly. They make several of the valves and you have to know which one you have. Mine was part # SM-IC-66R/WP28 (this number corresponds to how this particular switched is wired.