Sounds like a bad or oxidated reversing relay, as if you jiggled that around it did reverse for a while. We have a relay in stock, but before we send it out, you can test it with out taking the whole thing apart.
You can remove the cover of the relay (clear plastic cover), dont worry if you crack it, you can replace it easily or glue it back on. See if you can manually actuate the relay and cause the motor to reverse. see if there is corrosion on the relay or inside the housing of the relay. If you have some contact spray\dielectric grease that can help.
If after you recover the relay and try the machine again it still does not work - it might be one or more of the other components, or a bad\cold solder on the bottom of the main DC board, which happens over time, as the PC board degrades due to corrosion and oxidation.
See if you can test the relay and report back.