This is what I did to get it working:
-On the Android device, go to Settings->Apps->Downloaded->MediaMonkey. Then force stop, and clear data.
- then restart MediaMonkey on the PC.
- then Open MediaMonkey on the Android Device again and attempt to sync. It should work now
Hope that helps everyone else.
Some data that MediaMonkey stores on the Android device is conflicting with data on the MediaMonkey-client-side server. Clearing them both (by clear data and restarting of PC-MM) solves the issue. To the devs: I would code some sort of Expiration for this data after finding the culprit. Perhaps by timer, or by System Date. Refreshing the data after disposing of it should programmatically solve this issue for users.