Offline Prtoject loses Revision History - becomes unopenable

[ToriTait]

I have been using Projects - and ran into a problem where after a while (1-5 days) Offline Projects lose their Revision History - and become unopenable.

I have raised this as a case with Avid Support - who are being their usual slow and hopeless selves, So I wondered whether anybody else had seen this issue....?

This is with Pro Tools 2020.3 and now 2020.5 on Windows 10.

I have 2 Projects set up at the moment. These are clones which I have been using on and off since May 14th. I have shut down Pro Tools a few times, and restarted a few times, since the 14th. And I did have to re-sign into Pro Tools once during the period. But my PC has had internet access the whole time.

'Matthew Weiss - Coming Down' is a Cloud Project - it is working fine and has a Revision History
'Matthew Weiss - Coming Down (Offline) is a Offline Project. It had a Revision History yesterday when I looked - but does not have one now - and is now unopenable.

I am using the default Project Cache at C:\Users\<user>\Documents\Pro Tools\Project Cache

The Project cache contains two .ptproject folders - the first of which is the 'Matthew Weiss - Coming Down(Offline)' Offline Project.
The C:\Users\Audio\Documents\Pro Tools\Project Cache\UofPybm2lPqGKXmVxRrk7c\sC2eV-E-DdeTPoaWVu5wob#.ptproject folder appears to contain all the Offline Project information - including a Revision History.

So the Offline Project still exists, with its data and Revision History in the Project cache. Pro Tools read all of that from the 14th to yesterday - but now cannot find the Revision History - and cannot open the offline Project.

So that seems to say that

Cloud and Offline Projects work the same wrt the local Project cache
Cloud Projects sync with the cloud, Offline Projects do not
for Offline Projects, Pro Tools has a bug where after (in this case) 5 days it fails to reconstruct the Revision History from the Project cache - and cannot then open the Project.