Once again I take myself to have found a solution (but not via the forum that I mentioned above).
The seeming solution is detailed here on this forum. To wit: disable 'Show ghost files for queued copies'.
Perhaps though the above treats a symptom - wrong file icons until F5 - rather than the root cause. Here is why. I do still find that, when pressing F5 - which I no longer need to do in order to see correct icons - for some files the Sublime icon shows up very briefly and then disappears.