Dear Mr. memoli1478,
thank you very much for the quick and competent answer!
Of course my satellite scan was done with the multistream option, (I've been dealing with electronics since the 1960s after all).
In fact, it turned out that the data on the signal speed of the transponders slightly... differed from the actual ones, enough to fool both me and the receiver, which were indicated on the LyngSat site.
It took me a while to get the exact (real) speed data and actual beam on each of the transponders!
Now , everything is OK ! The receiver has no error!
Thank you again!