I received two MPS400s today for the two loops in my system.
Did the soft/firmware installation on the first one, physically installed it, and it works as advertised.
Did the soft/firmware (changed Aquabuss Address and loaded the calibration) on the second one, then physically installed it.
The second one leaks water from behind the metal plate. No visible cracks. And once wet it is no longer visible in Aquasuite.
Purchased from PPC, and sent a RMA request. Their reply was to ask for a picture, and said they would have to ask what AQ advises. A bummer to now be in the wait state for the second Flow Sensor. There have been reports of MPS leakage on other forums (just a few) so it's definitely a known issue/possibility.

RodeoGeorge