Today, I wrote this Quick First Setup Guide which give instruction about dealing with dual-sim smartphones in order to avoid - as much as possible - connectivity problems.
UPDATE
Moreover, having such guide allows everyone involved in supporting the hardware to have a standard starting point in order to reduce - as much as possible - the interference caused to a different setup procedure.
This is about the GPS availability for SFOS native apps and does not belong specifically to the reply to @jollausar.