Plot hole: Caroline helps Max get her degree, since Max didn't graduate high school. However, in episode 5 of season 1, Caroline and Max are raising money to pay off Max's student loans.
The Mothers - S3-E17
Plot hole: When the "refrigerator" falls on Tobias's mom, the boys are watching from a side view. It is later revealed that the fridge was just a cardboard cutout. The boys were watching from the side, so how did they not notice it?
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.