One monitor doesn't update when when using 2 external monitors

[MarkEstefanos]

Checklist

• I have searched for existing issues
• I have looked through the wiki
• I have updated MonitorControl to the latest version

Describe the bug
When using 2 identical external monitors, the sliders for both monitors only effect the first monitor, with neither slider ever effecting for the second monitor.

If I check "Change Brightness/Volume for all screens" the second monitor doesn't change at all when I change the brightness

When using only 1 monitor at a time everything works as expected with either monitor.

To Reproduce
Steps to reproduce the behavior:

1. Plug in both monitors.
2. Run MonitorControl.
3. Attempt to change the brightness on either.

Expected behavior
Each slider would effect its respective monitor.

Screenshots

Additional context

Environment Information (please complete the following information):

• macOS version: 10.15.5
• MonitorControl version: 2.0.0
• Monitor(s): 2x BENQ BL2711U
  Both using mini-DP to HDMI adapters

[MarkEstefanos]

Same issue with ddcctl.

./ddcctl -d 1 -b 35
and
./ddcctl -d 2 -b 35

both effect only the first external monitor. I also tried digging around the source of MonitorControl a bit to see if I could isolate the bug, but no luck so far.

[MarkEstefanos]

Looks like this is the bug I'm running into: kfix/ddcctl#17

[JoniVR]

Duplicate of #49