Thanks to a helpful advice of @gt6champnk69 I recognized that the original version with the really tight hairpins and chicane caused red laps in time trials and the partial disappearance of the racing guideline.
I've recognized the strange AI behaviour myself before but I wasn't aware of the negative effect on time trials or online racing either.
For that reason I deleted original version and replaced it by the AI compatible version I've had already created.
Now the replica may be a bit further from original but most important it should run properly.
I hope you enjoy Magny-Cours.