I can rarely flash my headlights without latching my mainbeam on and having to pull the stalk to turn them off again.
I assume this is a(nother) fairly common P38 thing, as both my own P38s have had dodgy stalks, and a bit of Googling brings up a few posts. Having a spare, I cracked it open and couldn't reliably get the flashing function to work without being unable to then trigger the 'main beam latch' buttons on the PCB. That may have something to do with me having read the wiring diagram backwards and I was testing only with a multimeter. So what I thought was the flash wire was the main beam, and vice versa.
Gave up on that plan having not realised, and decided I'd use the speed limiter button as my flasher control instead. I find the speed limiter relatively useless, given it doesn't limit speed, and setting the speed at which it beeps isn't great.
I actually made two attempts at this, as I cocked up and got it reversed the first time. On this stalk, during my attempts at spacing the mechanicals inside out to get the buttons pressing properly, I actually stopped the main beam button from being pressed entirely, yet seemingly managed to get the flashing pads working. I have no idea how I did that, but hey. That left me needing to swap the flash and main beam functionality around, which was easy as conveniently the flash and main beam pins on the socket are next to each other. So all you have to do is cut the leg at the bend on the second in pin, bend it over slightly to the left, and solder together. Then, take wire #6 from the PCB, and solder it onto the back of the pin whose leg you just cut.
Now I can flash by pressing the limiter button reliably, and a short or long pull on the stalk turns on/off the main beam.
I'll have another crack at repairing the now spare stalk, but it seems like a pretty poor design. Makes more sense on other cars that pulling forward flashes, pushing back puts main beam on...