Sub # off with RTC does not always work

Show Control RTC with Sub # off does not work if a fader with this subaster was manually set to 100%.
Only if Show Control RTC with Sub # on was used before, Sub # off will work later.
The direct console command Sub # out or Sub # AT #% always works, regardless of a fader with this subaster.
How can I guarantee that Show Control RTC with Sub # off also always works?

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