Ok, this thread can be closed.
I have to admit that if WH repair increased the reception quality, not everything is solved.
After having HW fixed my devices, they had a rapid fixes during some 5 -10 day.
Although The SAT reception signal is much better than before the HW repair,
My daily one needed > 20 minutes to get a fix yesterday.
Now that HW cannot be in cause,
this shows that there is also a real software issue with GPS in SailfishOS.
(Sky was clear, no buildings, last use < 24h, at least 10 green bars, custom settings On On Off.)