This happens when moisture gets into the pump electronics.
I completely disassembled the pump. I left it to dry for 6 hours and then, to ensure the effect, a little hairdryer to dry everything.
I finally put the pump back together and it seems to be OK now!
It was long, but the system is functional, the "leakshield" coupled with my "D5 next" pump (which makes no noise), ensures protection against leaks.
I took the opportunity to limit the 90° fittings on my loop and in particular those of the pump.
All I have to do now is clean and put the cables back in place, but I'm going to leave it like this for 48 hours to check that everything is okay!