.sesx file will only load from within Audition

Hi all

I have CC2021, 2020, 2019 and CS6 on a Win 10 pro build 19041.867 (which I believe is the latest).

The OS is set to use 2019 by default.  Up till a few weeks ago all 4 versions happily coexisted, and I could open a sesx file from file explorer and Audition would open and load the session.

Then something changed (probably bl***y Microsoft) and now I can only open a sesx file from within an opened 2021, 2020 or 2019 instance.

If I use "open as" from the explorer menu I can open the sesx only in CS6, the other 3 just open Audition ready for me to then open a sesx file.

Everything else is fine, all 4 versions behave as they should.

Obviously I have checked file associations etc and I am quite happy working in the registry.

My guess is that M$ have changed something and in their usual arrogant fashion decided not to tell the great unwashed.

Anybody had experience of this?  Its not life threatening, just frustrating.

Thanks

Anne