Steering problems continued after the trace fix.
These mounted as the weather cooled. The next idea was corrosion in the paw controller.
That didn't fix the problem, but obviously wrapping it in tape didn't stop the corrosion. Progressive failure of steering continued as the weather cooled. After a momentary loss of servo control, it regained its original heading, so the IMU was still working & the paw controller wasn't causing it to deviate. It always failed in higher elevations, never on the valley floor. That left a failure in the servo or mane board. The next idea was cleaning the mane board.
There's no reason for cleaning the mane board to make any difference because it wasn't affecting any other signals. The servo was rated as waterproof.
Another 30 miles in the cold damp didn't have any steering problems, so cleaning the board seemed to buy it some more time. Clenching PLA for 4 hours made the lion paws mighty raw.