Recording only one channel with interface units since 3.3.3

We have hundreds of clients we train using Audacity. Most were Windows users, fewer use Macs. When those using interfaces migrated from 3.3.3 to 3.4.0(+), we began to notice modulation problems in Mono recordings.

We began surveying those and found that their interfaces (Focusrite primarily) were recording on 1 channel clearly with the second channel recording at a minimal Gain. When rendered to Mono, the recordings produced high amounts of modulation - as if Audacity were adding Gain to the second channel in order to make up for the low Gain recorded. It continues to happen. We have tried to work around it using Control 2 software from Focusrite by Linking the two Analogue channels. Sometimes it works. Other times it does not work.

As the issue didn’t begin happening until the move from 3.3.3, we feel confident that something has been missed in the new releases that allows for this miscommunication between Audacity software and interfaces.

We have begun seeing it in other interfaces: Presonus, Zoom, GoXLR, etc and in both PCs and Mac. The common denominator is Audacity.

Can you assist with solutions, workarounds, or patches that will mitigate our findings?

Actual “modulation” (unwanted dynamic-changes in volume) is usually Windows “enhancements” (automatic volume control or automatic noise reduction, etc.). Or some computers/soundcards come with their own optional “enhancements”.

There is an “oddity” in Audacity - If you have a stereo interface and you record in mono the levels are cut in half to prevent clipping when the inputs are mixed. If you’re only using one input you can’t go over -6dB (50%).

The clipping indicators (or meters) on your interface are correct and if they don’t show clipping, you are not clipping.

If you are using one input you can record in stereo and delete the silent channel after recording to get true-mono (which will play from both speakers). Or you can record in mono and boost the volume after recording. (Low digital levels aren’t really a problem, especially at 24-bits.)

Focusrite Control MAY have a way of getting-around that, but I don’t know.

Thank you for your quick response.
We’re trying desperately to “work the problem.” We’ve used Sound Control settings in Windows to resolve some and - as you said - Focusrite Control or Control 2 in order to fix others. Macs are a whole other issue.
Many on YouTube suggest recording a stereo track, splitting it, deleting the “bad” track, and copy/paste the good one to complete the recording. While it works, it fails to fix the original issue - recording both channels properly.
The problem remains.