Sorry to say, I just went thru the same ordeal last week. You can tow 4 down but not 2 up with out disconnecting the drive shaft. Something to do with internal lubrication.
I had to return the dolly and buy a tow bar. I could have dropped the drive shaft but didn't want the hassel. Mike
Mike, Stacy,Preston & Dutch, our German Short Haired Pointer
2001 38.5' Dutch Star DP, 2015 Jeep Wrangler toad