Had the same thing happen to me a couple of years ago. Figured that one of the relay contacts, that short the motor to provide braking (and incidentally, provide the alternate ground to allow the motor to run in either direction) had burned bad enough to not make contact. Without that ground, the motor will run one way but not the other and will coast when de-energized.

When the motor coasts, it can allow the magnetic spot on the feed-back rod to get past the reed limit switch and re-energize the motor, driving it into the mechanical limits almost before you can get off of the switch. On the early flap mechanism (235 and maybe 320) if the failure is in the flaps up direction, the system will likely jam - the push-rod and flap lever will go just about over-center.

Turned out that a connector on a spade terminal on the relay had worked it's way off the contact - pushing it back on fixed the problem - but realizing what could happen if the relay really did fail, I now carry a spare.

Dan Schaefer
Early 235