Question / Help OBS monopolizes Magewell HDMI Plus and disables it for other applications

[mpjme]

Hello fine people!

I am using a Magewell USB Capture HDMI Plus connected to a Sony A7III as my face camera for my streams.
It is working great in isolation, BUT ...

Whenever OBS is active, other apps seem blocked from using the Magewell output.
I.e. OBS seems to want monopoly on the Magewell.

• Examples of applications that cannot access the Magewell output when OBS is active are ...
  • Quicktime
  • Skype
  • OBS (If I run another instance of it with "open -n -a OBS.app" in the terminal.
• OBS only monopolizes the Magewell, not other cameras. For example, OBS does NOT monopolize ...
  • Facetime camera on the Macbook
  • Logitech C920 (I connected it exactly the same way as the Magewell, in the same USB port)
• It's only OBS that tries to monopolizes the Magewell. Apps that can co-exist just fine, accessing the Magewell simultaneously are:
  • Wirecast v.11.1.0
  • Skype 8.34.0.78
  • Quicktime Player10.5 (928.50)
• Tech specs
  • MacBook Pro 2016
    • Mac OS X Mojave 10.14 (18A391)
    • 2,9 GHz Intel Core i7
    • 16 GB 2133 MHz LPDDR3
    • Radeon Pro 460 4096 MB
  • OBS 22.0.3
  • Magewell USB Capture HDMI Plus (Firmware 2.6.8257)

Any ideas why OBS monopolizes the Magewell output and how I can prevent it?