The majority of French supplies are "TT" i.e. they only have a local earth, but there is a power-company supplied RCD after the meter and 30mA RCD protection on most circuits in modern supplies too.
It's possible that you might have faulty earth electrodes, or they are inadequate.
I'd strongly suggest getting a French electrical contractor to take a look at it. There's really very little a DIYer can do to sort this out and it needs proper testing.
If it's an old installation, anything is possible!