Because of an oil leak I planned to replace the boken rocker cover (cache culbuteurs in french). I saw in old topics that is magnesium oxidation.

Spending days online to get the two replacement covers I finally got new ones from aliexpress (!). Thank you to the guy who shared this info on the forum !

Just received and they seems to be real good quality.

Replacement should be done by the mechanic in 10 days, I ll update this post.