When Mack slashes Vulturus in half and he explodes, large chunks of his body are left as debris, littering the battlefield. Yet he's back in one piece, wandering around the city in the next scene.
It's implied that the returning Rangers are repowered permanently, so how does Kira's Dino Gem wind up abandoned and depowered in time for "History"?
Alpha 6 is notably taller than in any previous appearance. Before, he barely came halfway up most Rangers chests; now, he's only a few inches shorter than Adam.
It's never explained how Bridge came back in time, nor how he'll be going back to the future. It's obviously due to Sentinel Knight's powers, but it's never stated. Not to mention, previous times an SPD Ranger has time traveled, those they met would have their memories erased. Bridge makes no mention of needing to erase anyone's memory here.
How and why did Alpha 6, last seen living with the Lost Galaxy Rangers on the planet Mirinoi, end up deactivated and stuck in a crate in Angel Grove?
Adam fails to use either his Power Axe's Blaster mode, or his Blade Blaster, when all of the Rangers are using laser attacks on the villains.
Bridge's genetic power had a green aura originally, but it seems that changing Ranger colors must have changed the aura color.
The Sentinel Knight said he restored all the former replacements powers, but SPD's powers were never destroyed so he shouldn't have had to restore them.
If Sentinel Knight was going to go to the trouble of restoring Adam's powers, wouldn't it have made more sense to restore the Black Ninja, Green Zeo or Green Turbo powers, rather than the weakest set of powers he had?
Tori isn't wearing her "sensei" uniform that we last saw her wearing in "Thunder Storm" Parts 1 & 2. She is wearing her Wind Academy Student uniform. You can tell because the Wind Academy symbol isn't in the middle of the chest.
Whereas all the other Retro Rangers have their season's instrumental theme music play when they first appear, Adam doesn't have the instrumental of "Go Go Power Rangers" play when he appears. This is because Haim Saban still holds the rights to the songs he composed with Shuki Levy under the Saban Records banner. Since the budget was already stretched enough getting the past cast and uniforms for the two episodes, paying the royalties was not an option.
If Thrax is Rita's son, why didn't the Sentinel Knight have Xander contact the Mystic Mother (supposedly Rita) to stop her son?
Why didn't Sentinel Knight just recruit Rangers that still possessed powers and Zords, instead of going for Rangers currently powerless or in the future? Surely Wes and Eric, or the Lightspeed Rangers, even the Space Rangers, would have been willing to help.
Why didn't Sentinel Knight merely repower the Overdrive Rangers, if he could do so to Adam and the others? Similarly, why spend the energy going 20 years into the future to get Bridge when other Rangers from this period are more widely available?
Thrax appearing as old as he is, isn't that much of a goof if you factor in the idea of aliens aging faster than humans. Rita & Zedd only got married in 1994 from the show's standpoint. But how is it he's the same age as he is now "years ago" when he's imprisoned by Sentinel Knight?
Andrew refers to San Angeles as "San Anges".
At the start of the second battle with the Fearcats, Mack told Spencer to send all the Zords, however the Sonic Streaker wasn't sent.
Just like the first and second jewels of the Corona Aurora, the third jewel is no longer in its diamond shaped form that was seen in the flashback in "Kick Into Overdrive (1)". However, this is the first jewel to have one of the original five colors.
Why did it take so long for Tyzonn to show up for the battle? Will was the one who was given a reason to be late, he wasn't.
Ronny's lucky socks go from large, oversized tube socks (too big to fit her comfortably), to smaller ankle-sized socks, when Red Ranger wears them in battle. They return to their larger size in the final scene.