Having checked the original file before WinSCP sees it appears it does indeed have the BOM included on its own. To do this i had to use the internal editor of WinSCP from version 5.5.1
I am using SFTP protocol in both cases however i had made a mistake in the revisions. The new version is indeed 5.5.1 however the old version is not 5.1 but is in fact version 4.3.5 build 1463, apologies.
If I transfer the same file from the same location using version 4.3.5 and then open it with the internal editor of 5.5.1 then the three characters do not appear when the encoding is changed between UTF-8 to 1252 ANSI latin 1 and back again. However do exactly the same with version 5.5.1 and they do.
I have enclosed two images from both versions showing the Editor page.
In version 5.5.1 I have tried the transfer with both 1252 ANSI chosen as default and then UTF-8 with the same result.
Is there anything else you could think of I could try?
We upgraded from version 4.3.5 to 5.5.1 in order to fix an authentication problem and the new version allowed us to use the switch
-hostkey="*"
after the login process to solve that.