I have this same problem. Tried 2 different computers, 2 different sound cards, 2 different USB cables, 2 different wall sockets. Problem persists.
Had a Mopho with USB, this never happened.
Set up 1 - iMac. Motu 828 MK2.
Set up 2. Macbook Pro. Motu Ultralite Mk 3.
Is this a known deign flaw? Should I return the synth to the shop and get a new one?