This shot is more than likely Sentai footage which is likely why it's so quick because they had to end it early
All shots of the Rangers witnessing the Magna Defender is new footage. Any time you see the Magna Defefender in the same shot as the Rangers who are watching him as he exits the Cave is new footage.
Here's Treacheron in the Scorpion Stinger

The footage of Starcog in the Cave is new footage but you never see his suit on-screen at all which leads me to believe MMPR Productions might have never gotten the suit and the editing was just some kind of trick but then again who knows.
Here's new footage of the Red Ranger with some kind of Stone
Here's Ruptor in new footage

Here's new footage of the Magna Defender while he's armed with his Magna Blaster

Once you see Samuron then it's the start of Sentai footage.
These shots
are back to new footage but once it cuts to this shot then it's back to Sentai footage.
Once Samuron calls for Stingwingers, it then cuts into new footage of the Magna Defender
Here's anotther shot of Stingwingers
Here's new footage of the Magna Defender with his Magna Sword
The following shot of the Red Ranger talking to himself is when it returns to Sentai footage.
After the Stingwingers are dealt with, the Magna Defender continues to play in Sentai footage.
Here's new footage of Treacheron
All of the flashback is a mixture of Sentai and new footage. All Treacheron stuff in the flashback is new footage however any shots you see of the Magna Defender alone in the shot is actually Sentai footage.
This shot is more than likely Sentai footage
You see Ruptor drink the green liquid and then it cuts into Sentai footage of him growing.
This shot is new footage.
All following shots of the Rangers including the shot of the Red Ranger calling for the GalactaBeasts is new footage.
It then goes into Sentai stock footage of the GalactaBeasts arriving sequence which is when the Sentai footage returns.
Here's new footage of Treacheron's Sword
All Samuron footage is Sentai footage. You do see his Hammer briefly in new footage though but you never see Samuron himself in new footage.
All Treacheron footage in this episode is new footage.
The fight between Treacheron and the Magna Defender is all new.
Once the ep returns from the last commercial break, the ep returns with new footage playing.
Once you see Magna Defender in midair then that's Sentai footage of him.
This is also Sentai footage of the Magna Defender
Any shots of the Rangers being in the same shot as the last shot that I have pictured there of the Magna Defender is Sentai footage but the following front shot of the Rangers when Leo is saying he thought for a moment he (the Magna Defender) may have been his (Leo's) brother but he guessed he was wrong is new footage.
The up-close shot of the Magna Defender when he's saying nothing will stop him is new footage.

Ruptor Sentai footage which is just its Giant footage comes from Ginga Episode 8 whereas the Samuron footage comes from Episode 18