You need to be a bit more specific. If it's a new install, then it sounds like a wiring issue. Those cheapo two-pin plugs are prone to issues, so I'd suspect that.

I swapped Stu's quickshifter (as a warranty exchange), and the brand new one was exactly the same as the old one. So it's not the unit. I put his old unit on one of my bikes, and it was flawless. So it's the wiring. Either the plug or where the wires join the switchblock wires. Adding a coil harness just replaces both of those potential problem areas.