Some further information…
Brian mentioned that he had not seen any other reports of my issue.
One possible explanation for that is that I am on satellite internet. I am on the relatively new Australian NBN satellite system which is a vast improvement over previous satellite systems I have been on.
I hesitate to mention this these days as many IT people immediately blame the satellite internet and then won’t do any further investigation.
in around 2 years usage I have never found any other software or system that does not work properly on the NBN satellite!
Download is 25Mb/s, upload 5Mb/s and the ping is reliably around 570 mS which is close to the speed of light travel time for the distance involved (around 150,000 KM return trip)
However, of course, the satellite system and the long ping MIGHT have something to do with it. Perhaps the newer Clientrawrealtimeftp might have tighter timing requirements??? I’m only guessing!
Also the administrator of my new webspace gave me the link for the FTP instructions for their system which I thought might be of interest.
https://docs.microsoft.com/en-us/azure/app-service/deploy-ftp
I just thought this information might be of some use.
Thanks again to Brian.
Ian