Hi, thanks for the reply. What is the locking files issue?
The file appeared to be the correct (latest) version by the date and time, but the content of the file was corrupted. i.e. Lightroom reports "this catalogue is corrupt and can't be opened' This has happened severally times. I could imagine part of the file is synced incorrectly while Lightroom is open and writing to the file, but surely once Lightroom is closed and the final file is synced the files on each computer should be identical?