Strange MIDI problem. Help!

Sorry, new to the forum but have been using Cubase for quite some time.

I have the following problem - load a VST instrument, i.e. Omnisphere or East West Orchestra and when I play G4 on my MIDI keyboard (Impulse 25) the volume of the instrument drops either considerably or , in Omnisphere, all down to zero. It is not a Novation problem because it is not doing it in Ableton or in other software I have tried. It is not even a mechanical problem (defective key) because if I transpose the instrument, the mistake “transposes” to another key on the keyboard.

It ONLY happens on G4 and visually, on the plugin interface’s keyboard it looks as if the key is permanently depressed.

So, by excluding all other causes, I have come to the conclusion that the problem is with Cubase. It messes my workflow because I input parts in my sequencer by playing them. The only remedy I found so far is either reloading the whole instrument patch or having to go each time and move with my mouse the volume slider up.
I am running both Cubase 10.5 and Cubase 11 on an iMac (see image for system info) and I am using UA Apollo Twin.

Any ideas?

Screen Shot 2021-04-28 at 4.12.32 PM

One of the ways this kind of thing can happen is if, the remote control keyboard is wrongly connected/configured with a Cubase Remote Control (Quick Controls, Mackie, Generic Remote, etc.)