It's hard to have complete answers without being in front of the unit.
If it is only on engine A, it would indeed suggest that the problem is in the unit, although there is a (small) chance it is down to the way it is being used.
But, your recordings suggested that it was very much worse when being fed by the Motu. Yet again, this could be due to different noise levels triggering different glitches.
Basically the units need to be looked at – I've done all I can from a distance. I am in touch with Sound Service and am waiting to hear what they know.
