I use about 4 soft synth modules. Of course, each of these has volume setting built into the face. Obviously, I have a MIDI channel (with a fader) assigned for each synth too.

For some reason, on one or two synths, when I try to adjust the Cubase mixer fader for that instrument, it is not effective. Currently, if I want to adjust the volume, I am forced to do it through the instrument's face.

From time to time, this may have happened with more than one soft-synth. What is happening here & how to I get this problem-synth’s Cubase mixer fader to respond like all the others?