Hello guys.
After many months waiting for parts, bench availability and so on, I wanted to share with you the result of the investigations : at last, the culprit was the brake limiter.
My mech tried to find another part, without succeeding (it took him months... for nothing). He replaced it by two single limiters (one on each front line), setting them up on a rolling bench.
By far not the smartest way to solve the issue from an engineering point of view, but at last it works, and now my Pantera brakes w/o pulling.
Nonetheless I kept the OEM limiter, because I read somewhere that it could be recommissionned. Later, maybe...
Thanks again for your information and help.
Matt