Ride truncated and now disappeared

I did a ride this morning.  When we stopped for coffee I was removing the computer from my bike and I saw it was restarting (not sure if I accidentally pressed some buttons to cause this or not).  When it restarted it offered to recover the ride which I accepted but I noticed that the distance shown was around 10k lower than it should have been.  When I arrived at home I saved the ride as usual but it didn't upload to Strava.  I've tried everything I can think of to resolve this to no effect and now I can't even see the ride on the unit itself.

Things I tried:

Restarting the unit

Opening the ride and clicking the Strava icon to upload it

Enabled USB debugging and mounting the device to different computers (Mac, Chromebook, Windows PC) but the Fit files directory is not visible on any of them.

Factory reset of device.  After signing back into my Hammerhead account this identified there was unsynced ride data and offered to correct this.  I tried that and now the ride doesn't even appear on the device any more.

I've had my Karoo2 for over a year now and this is the first bad experience I've had with it.  Hopefully someone can give me some pointers to fix this?