Not sure what is going on, then.  It works as expected here: version 1.3.0.75.  Tested using a MIDI Baby 3, Source Audio Reflex; I expect the FCB-1010 here, or CC#0 via DAW Transmit will yield the same results.

I even tested Aux switches to see if they might diverge from MIDI; as they have mirrored parameters in Global Mapping.  Works the same.

Unfortunately, there is no Learn function in Global Mapping, like there is with individual parameter control.  Makes for a great test to confirm what you’re sending is getting received by the H90.

You could try sending CC#0 to (any) parameter, using Learn, to see what happens there.  Without narrowing down the range, you should see (any) parameter snap between minimum & maximum values.

Better still, a MIDI Monitor would give you back exact CC Number & Values at a glance.