This isn't my area of expertise, but this doesn't look right
16:18:52.169: Device for 'Audio Output Capture' source Desktop Audio is also used for audio monitoring.
16:18:52.169: Deduplication logic is being applied to all monitored sources.
16:18:52.169: [win-wasapi: 'Desktop Audio'] update settings:
16:18:52.169: device id: default
16:18:52.169: use device timing: 1
16:18:52.170: [Loaded global audio device]: 'Desktop Audio'
16:18:52.171: [win-wasapi: 'Mic/Aux'] update settings:
16:18:52.171: device id: {0.0.1.00000000}.{eaa8e531-b5a4-458e-880b-7d534af4fac7}
16:18:52.171: use device timing: 1
16:18:52.188: Device for 'Audio Output Capture' source Desktop Audio is also used for audio monitoring.
16:18:52.188: Deduplication logic is being applied to all monitored sources.
16:18:52.226: [WASAPISource::TryInitialize]:[External Microphone (Synaptics HD Audio)] Failed to initialize audio client: 8007007E
16:18:52.226: WASAPI: Device '{0.0.1.00000000}.{eaa8e531-b5a4-458e-880b-7d534af4fac7}' failed to start (source: Mic/Aux)
OBS Studio will, assuming you know what you are doing, let you set up a config that often won't work
Capturing Desktop Audio makes sense, BUT then you have to manually (usually physically, like headphones) ensure your don't create an audio loop. Sorry to say, that is 100% on you to understand, and avoid. A mic that gets fed to Desktop Audio that is output on a speaker also captured by mic is an instant loop.