This time, the front wiper does not work properly.
You may read almost evreywhere, Google is your friend....
About this matter, it seems nobody ever went deeper, and to my issue, which seems to be quite widespread, Google wouldn't helped that much; the only answer I found by it is "change the motor and its controlling circuit". This solution can be quite expansive, looking around for prices, it seems you can not find it for less than 100€.
On the other hand, looking at the controlling circuit, it does not seem to be very complicated, so I decided to use some time to resolve my issue, and therefore save 100€.
I also made some schemas to help myself in understanding its behaviour.
Well, I guess this is the time where I tell you which is my problem, after all.
Problem is as follow: the "SLOW" speed of the wipers does not work, and when it is set to the "FAST" speed, if you turn off the wiper it stops where it is, without return to its home postion.
After several hours of analysis, I found where the problem lies.
It is due to the oxidation of the normally open contact of the relay.
This way I saved myself more than 100€ for the spare part, I hope anyone else could found my info useful and save his money.