Plot hole: We learn the rangers were pre-selected to join the team and were in waiting until called to duty, but the yellow rangers sister just passed the legacy onto Emily, who was only a child.
Plot hole: This was the first episode of the series and we see that the rangers are unable to figure out how to properly operate their zords; but in Origins Part 1 (which takes place prior to this) they have no issues with the zords at all.