A slightly longer phase to get a first position may occur if GRETA has not been moved for a long time. In this case, the tracker was in a sleep mode. Now it is possible that when returning to active mode other GPS satellites are visible than before. This means that GRETA first has to reorient itself and interpret data to determine a position.
Imagine sleeping and waking up in a different place. Now you probably need to reorient yourself to know where you are. This is similar to when GRETA wakes up from hibernation and finds new GPS satellites.