@KeithRJ thank you for that suggestion things went from worse to even worser (worse).
Plan X (NAS):-
My NAS drive(s) are mapped on my systems as X: and Y: and I have never had any problems synchronising to them or opening files on them in the past (you know what is coming). I configured T and M to use a database on the X drive and attempted to start M (after configuring and restarting).
PL5 reported that it could not acquire write permissions on the database file on X. In a later attempt I saw a new database file appear on X when I changed the database location but it still said it could not acquire write permission after I re-opened it! Changing PL5 to run as ‘administrator’ had no (positive) affect! It might be something to do with the permissions on the NAS drive but no other device has any problems accessing files on the drive.
I have abandoned Plan X for the time being (NAS is DS220J and PCs are WIN 10)
Plan M(ain):-
So I attempted to do the suggested NAS tests but with the database and the photos located on M. I opened the database on T and navigated to the V: drive (mapped to F: on M) changed one file to no noise reduction and closed T down.
Opened M and navigated to the same folder and Virtual copies instantly.
While PL5 on M is running I attempted to open PL5 on T which hung so attempted to close PL5 on M which also hung and finally dumped after which T could access the files and yet more Virtual Copies were made. Looking at the snapshot I believe that of the VCs [M] is the change made on T, [1] is the original that was on M and [2] is the one from T!
Plan S(pare):-
I have another (Win 10) machine that I could try as a NAS replacement to hold the database and the files in one location and then access from M and T to the mapped drives of S(pare) (the “only” complication is 3 machines and only 2 screens so I will need to do screen switching and keyboard switching - in fact I started to type this last bit with the keyboard attached to the wrong machine)!!
So M is pointing to DB on S, T is pointing to DB on S and while T is up after the DB switch restart I changed 2 photos to DeepPRIME in directory on S and closed T. Started M and navigated to directory on S and all O.K, no VCs and 2 photos with DP. Set ‘Reject’ flag on one photo on M. Closed M and started T, one photo with ‘Reject’ flag so set another photo with ‘Accept’ on T and closed PL5. Opened on M all O.K. and ‘Accept’ flag on as expected. Started PL5 on T and hung so terminated. Attempting to close PL5 on M hung and finally dumped!!
This is similar to the test I ran earlier except that both the database and the photos are held on the same device which is not running PL5, PL5 is accessing this third machine from two other machines across the LAN. The issue with the NAS has got to be some permissions issue!!
The excitement of all this almost exceeds the excitement of Christmas or dodging you know what!!