Plot hole: How were the Rangers (minus Jason) able to form the Megazord if Jason wasn't there to summon the Tyrannosaurus (not to mention Jason's morpher being in Goldar's possession)?
Plot hole: Quite often the Rangers were contacted at school and would teleport to the command center, danger zone, etc. It is safe to say that the faculty would notice star pupils missing classes so often, yet it was never questioned or addressed.
Plot hole: During the Green Candle, in series 1, we are told that the only reason Tommy's Green Ranger powers could be drained is because he touched a special wax. However, Kim, Billy, Zack, and Trini did not touch the special wax, therefore the candles shouldn't have stolen their powers. When they were captured, they were transported straight to a prison cell as Goldar lit the candles, therefore the Rangers couldn't have touched the candles when captured.
Other mistake: In the scene where Tommy is proving himself to Goldar on the beach against the putties, Tommy stares down the last remaining putty and makes a charge towards him. In the wide shot of Tommy charging towards the putty, one of the "dead" putties on the ground lifts his head off the ground slightly, almost as if he is watching the action unfold. (00:09:05)
Other mistake: After the teens leave the command center, Rita sees this and orders the creation of her Putties. Her henchman slaps down a few things of clay into a mold loosely, that then show the perfect figurines of the putties coming out of them. However with the shape of the mold, there is no way that the clay would come out in shapes like that or with that detail. (00:11:35)
Character mistake: About halfway through the episode, we see Billy, Zack and Kimberly are frozen because of Shell-shock. Towards the end when Jason and Tommy are in the Zords fighting Shell-shock, the Yellow Ranger comes running with the flowers that unfreeze the Rangers and Zords. The Yellow Ranger yells "Jason, Billy, I have the Diandra flower!" She should have yelled Tommy's name instead of Billy since we know Billy is frozen and that Tommy is the one helping Jason fight Shell-shock.