I would say the big one for me in The Last Jedi is hyperspace tracking. Just before the First Order ambushes the Resistance fleet, we see Leia show Finn that she has a homing beacon on her wrist, so that Rey can locate the fleet through hyperspace. This is what you would call a passive tracker, and it's been used in three previous SW films(ANH, AOTC and Solo). Seconds after this, the ambush happens, and Poe is the first to say that it's impossible, followed by this exchange:
Leia: They've tracked us through lightspeed.
Finn: That's impossible.
Leia: Yes. And they've done it.
The issue is that being tracked through lightspeed hyperspace is not impossible. It's commonplace since the Clone Wars. The accurate response to seeing that their fleet had been followed would be to say, as Jango Fett does in AOTC, "they must have put a homing device on our hull". And the characters know this, because Leia is wearing a homing device on her wrist that she just showed to them 10 seconds ago. That's a hyperspace tracker.
I can hear the naysayers now:
Did you even watch the movie? They're talking about active tracking, tracking without needing a beacon on board! It's active tracking that they are calling impossible!
Yeah, no. Poe says it's impossible as soon as they show up. Followed by Leia and Finn, and later, Rose. They are all faced with a situation that many of them have seen before, that is easily explained by passive trackers just like the one Leia has. A first step would be to turn that off, and then run scans on all four of your ships for homing beacons. Instead, the script requires them to act shocked to their core that such a thing has somehow occurred. Leia then proclaims that the impossible has been achieved by the FO, and the plot proceeds with a plan based on this lucky guess.
