Ok thank you guys !!

I did what you advised me @Facinat

, I excluded claymore files in Windows Defender but I think I'll have to give the Claymore 11.7 folder as recommended @Call_Me_Bambi

, Windows Defender had to delete the file EthDcrMiner64.exe, I am not next but I will do it and you will be redirected, there is no reason that it is not ca! it works since more the last release of version 11.7.
Thanks guys ! :-)
It was after a couple puzzling shutdowns of Claymore before I figured out what was happening (a long time ago).
I think this tip should be marked as a 'sticky' as it has caught out so many people, and not only with Claymore but other miners too.