The Protector of Concord Dawn - S2-E12
Plot hole: Sabine stowed away onboard the Phantom by hiding under the trapdoor in the shuttle's floor. That entry is just a single hatch, with nothing between it and the vacuum of space when the shuttle is flying. There is no way she could have hidden away there for the trip through hyperspace from the Phoenix Squadron fleet to Concord Dawn.
Plot hole: Dillon was quickly identified by the city sensors as having metal parts, thus classifying him as a threat to the city. Yet Tenaya, who is essentially a cyborg, tries out for the Green Ranger without setting off the same sensors.
Suggested correction: Tenaya wasn't caught because the guards assumed the equipment was faulty. It was giving positives all day because of all the sleeper agents we find out about later.
Plot hole: Cadmus sets a brain-controlled Connor loose in public, without apparently remotely considering the possibility that anything might go wrong. When he regains control all they've got is a few goons onsite armed with regular ammunition - what did they think that would achieve? They know exactly what he's capable of. Either have kryptonite ammo or don't bother having anyone there at all.