At Sparsholt I spotted this on the 7mm NGA stand:
Branded Keykits I guess it's pretty old, but it looks like a Wrightlines motor bogie, which is currently unavailable (like much of the Wrightlines range, sadly). It's essentially a Tenshodo motor bogie replacement, but with a Mashima motor mounted with it's widest dimension vertical to allow the wheels to be pushed in to 14mm gauge - very useful given the number of 7mm scale kits that utilise the Tenshodo unit. This one had crudely fitted pick-ups, mismatching bolts and a broken wire - but the motor turns when it got power.
It didn't take long to dismantle. I checked and adjusted the wheel back-to-backs, and found some M2 bolts that were a good fit - the nuts are secured with Araldite. I moved the PCB down away from likely body fitting and closer to the wheels, and attached new pick-ups from phosphor-bronze strip - which I find much springier and more effective than wire. With the motor refitted, wires reattached, and keeper plate bolted in place the unit was running.
Now I know these things can be a little fast, with relatively high gearing, but a few lumps of whitemetal on top slowed it a little. The motor seems to run quite hot too, I don't know if it could do with more airflow. However it dos occasionally stop at low speeds, seemingly at the same spot, and I think more of a mechanical bind than pick-up issues - though I can't see anything wrong with the gears. I'm hoping some running in will help.