USB compatible (or not) devices list

[Lizard of Oz]

The MRCC host ports nominally work with devices that are MIDI Class Compliant, however USB seems to be particularly complicated to apply correctly, and we often see devices that claim to be class compliant which still have incompatibilities due to the way they were implemented. It's not something we can change usually since it is to do with the device trying to connect

So you're saying it's a bug in the Synth. How can you rule out that this isn't a bug in the USB-host of the MRCC? From the outside, this were to look exactly alike, right?