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did you use a shim in the front lever (when you removed and installed the handle bar controls)???? if not, you probably damaged the tit on the switch..
The most frequent cause is the front brake light switch. Power up the bike and see if the brake light is on or if just barely touching the front brake lever triggers the brake light. If the brake light illuminates with almost no front brake lever movement then normal vibration and road texture will make the brake light flash, thus turning off the cruise. There is a small plastic "button" on the lever end of the brake light switch which is extremely easy to break off. Lacking the thickness of that button makes the switch plunger right at the make/break position and your brake lights will flash and turn off the cruise with bumps and vibration.
When I broke mine, I glued the head of a small plastic bolt onto the end of the switch plunger and it has worked fine ever since. The other option is to replace the switch, expensive and tedious.
One other possibility is that if you have had the switch box apart, the little sheet metal V shaped spring which pushes the switch against the lever side of the switch box fell out and the switch is now further recessed into the switch box. I have never checked to see if that little spring is available by itself.
All of the other answers are correct and valid but this is the highest probability of being the cause.
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