In the BTT Remote settings under "General" you can disable the "Volume Buttons" setting. Afterwards it will allow you to change the volume again but you won't be able to trigger BTT actions using the volume buttons anymore.
But if I want to use volume buttons on BTT remote, how could I manage with its curious behavior? The problem occurs regardless of whether there are or aren't volume buttons action on BTT of the Mac.
Anyway, currently I won't use volume buttons and I can disable it so it's not an issue for me.