Audition CC 2017 - Session can not be saved

Hi guys,

I am working in a larger session for two moths now. Since last week Audition tells me it is not able to save the session, because it is used by another application. (The inculded files can successfully be saved anyway.)

When I close Audition and re-open it the sesx-file looks like changes are actually saved, but the messeage still appeares and I would like to have certainty that the file doesn't get corrupted in any way.

Yesterday I upgraded to Audition CC 2017 hoping this might help, but the problem still remains.

I would be very thankful for any support.

Cheers,
Marc