I doubt its a bug, its more likely a config issue. If the unit encounters conflicts it will reboot. I havent had a reboot yet accept when I had conflicting aquabus IDs on the PA2s or once when I had corrupt data in the A5 after a firmware update.
It seems some of the data structures may change between upgrades and its best to reset everything to defaults after a firmware upgrade. Its a pain but it sorts out the kind of problem your experiencing. Before you reset everything though, just check you dont have any conflicts on the Aquabus.