There are no obvious failures with the save – appears to complete OK and the save date/time is correctly updated when viewed in Explorer. All projects are in the same folder. The subprojects are displayed correctly prior to the save but when I close and re-open the consolidated project they have disappeared. I can add them again OK but the same thing happens on a subsequent save.
As you say, something must be going wrong with the save but it’s very strange – I just wondered if anyone had encountered this before and had a solution.