I didn't take offf till I had more than 12 satellies, between 7 and 15 seconds multiple warning about no or weak GPS, that seems odd to me?
Having 12 satellites doesn't guarantee full GPS reception.
If you were flying a Phantom 1 or Phantom 2 from back in 2013 or 2014 it would have.
Back then your drone would have only had access to the 24 or so US GPS satellites orbiting the earth and receiving signals from 12 would have given you good coverage.
But for the last 10 years DJI drones have received signals from more than just one GNSS constellation.
All current models receive signals from 3 different GNSS constellations which have a combined total of about 80 satellites.
12 sats out of 24 = good GPS but 12/80 isn't good at all.
The number of sats you have does not ensure good location data.
You need more than a minimum number AND the satellites have to be spread over a large part of the sky to ensure good location data.
When you launched with 13 sats, the Flight Controller was rating GPS data reliability at 4/5 and had recorded a tentative homepoint which it would update when better data quality was available.
But from 7-15 seconds you were seeing GPS signal weak messages as the GPS data reliability was flickering between 2/5 and 4/5.
It wasn't until after 15 seconds that it showed a steady 5/5.
Rather than thinking that 12 sats ensured good GPS, you should watch the satellite icon in the upper right of your screen.
Watch for it to change colour from red to yellow to white to tel when you have good GPS data.
Sometimes the number of sats to achieve white could be 12, but more often it will be a number closer to 20.
There is no single number that signifies good GPS - you have to wait for white.
