2 years on and it seems Cubase 10.5.12 has the same problem (unless someone can enlighten me to another possible cause for the below issue).
Each time I reload my song project, the volumes for each VCA fader in relation to each other seem to change - I’m fed up with adjusting pointlessly so I will go through the exercise to scrap VCA faders and use groups.
The only downside I know of with groups (vs VCA FADERS) is the sends to the reverb on Stereo Out channel will still be heard when group fader is zeroised.