OK, I've done some more testing.
Seems like the problem is something to do with how the directories are checked AFTER the HTPC resumes from standby.
(In the examples below, all the changes to media files are made directly on the server, not via the HTPC).
If the HTPC (and MC14) is running when changes are made to media, then they are picked up OK.
If the HTPC is in standby (S3 in my case), and changes are made to media, when the HTPC is resumed, the changes are not picked up, AND, no further changes are picked up, even if the HTPC is running when the changes are made.
If I then run Auto import, the previous changes are picked up, and subsequent changes are picked up automatically.
It's almost as if going into standby, puts the drive and MC14 out of sync and an Auto import is needed to reset it.
Sooooooo
It would be nice to know if this is something that MC14 could do automatically, or whether this is a Windows/networking bug.
NB, in the past I have made a feature request, for there to be some options for how MC behaves after resume from standby. At the time, I wanted just to clear the playing now queue and go back to the Theater View Start menu. Maybe this is something else that could be added if this was ever done. If this has already been done, and I've missed it, I'm going to feel really stupid......
In the meantime I'm going to write a little batch job to run the auto import at resume from standby, and as a button under Theater View. Did I hear someone say belt & braces......