They all also run an instance of MMSSTV (ham radio slow scan tv software) and each time a new picture is received WinSCP uploads it across my network to my web server.
The instance in question will initially scan the directory and then upload any new files it finds- after that it is pot luck whether it bothers to upload any new ones. Mostly it just sits there telling me "Change in Y directory detected" but not doing anything about it.
All 5 systems use the same version of Windows 7 embedded, and as far as I can tell, all are set up exactly the same. To complicate matters, just occasionally it will continue to upload new pictures as they come in for a while before then reverting to ignoring any new ones.
In all 5 instances WinSCP is version 5.21.5 (Build 12858 2022-10-06)
Any thoughts or suggestions gratefully received!