Fair enough. It might not be possible to have a VST version of the MCC though, I suspect it really does need to be a standalone app which interfaces directly with the hardware, rather than through a DAW, in order to gain access to the firmware. This could be why the results are unpredictable when you have both a DAW and the MCC open, because they're both trying to shout louder than the other to gain exclusive access to the MatrixBrute.
I've always found the MCC to be buggy regardless. For example, changes that I make to the setup of my KeyLab 49 mk1 via the MCC don't survive a power-off/power-on. Even if I make doubly sure I've followed the instructions precisely, the controller always goes back to its default settings after a power cycle. Consequently I gave up using MCC for anything but flashing it with the all-too-infrequent firmware updates, and instead I make any changes directly from the controller's own panel of buttons. That's way more fiddly, but the changes are at least saved properly. I realise that's probably not a solution for you
Good luck in your quest for a reply from Arturia.