Duplicating MIDI instrument channels in the Mixer

Hardly anyone opens MIDI in a Mixer, however it duplicates MIDI channels when adding new musical instruments. I am worried that this may cause an error that will result in the loss of project data.
When deleting a instruments, duplicates are not deleted.

Dear developers! Help, please! How to fix?
The video file shows the problem.
Doubles MIDI channel in the Mixer.zip (1.07 MB)

This isn’t how Dorico behaves for me. If you choose Play > Playback Template and reapply the default playback template, are the MIDI faders removed?

I can’t reproduce this either. You shouldn’t need to worry about losing data - the only data that’s stored for that MIDI fader is the level and the pan.

Hello, Daniel!
Thank you for responding to my problem. I have already been able to fix this problem in this way. I had the Silens template installed. I had surgery to re-re-elected template - all OK!
Thanks again!