None of the "Answer" above was a solution to my problem having already tried all that so:-
I have a copy of the 1703 build that I can dual boot, I always have a fall back position to cover most contingencies, so I copied all the FX***** files from the older version which can be found in Windows/ System 32, *renamed all the existing ones to include the word old and then pasted in the 1703 version files.
You may wonder why the use of "sfc /scannow" and even the use of DISM Tool to check for errors failed to find a problem, obviously not a corrupted file??
*You will run into "permission" problems here and I used a piece of software called Take Ownershipto do so but some still could not be renamed so I ignored those and replaced the ones I could rename. Fax now worked so the unreplaced files would not appear to be the problem. I could have run a comparison between the old and new to see what was different, but I spend too much sorting out other problems so I am just happy that it worked
I have copies of both sets of files if someone is interested enough to find the actual fault.
I now await the next quarters build to see what happens. 1709 would not install so I had to do a total reinstall and if it happens again the air is going to turn black and a deadly invader will nuke Microsoft before being beaten off by the Avengers.