Plot hole: Sarah turns up on the bridge to fight the Rev-9, we later learn that she is texted the location of where to be as when the terminators travel though time it causes a gravitational anomaly, and this is where she needs to be. The Rev-9 had been there ages killing Dani's dad etc, Sarah would have no idea to be on the bridge after the terminator has chased them though the town - she can't possibly know that location.
Continuity mistake: When the main characters first meet up with the old terminator at his residence, Sarah tries to turn her shotgun on him, but is stopped. Instead, the round goes off punching a hole in a wooden ceiling of the front porch. The resulting debris lands on Arnold's T-shirt, standing out because of the T-shirt's dark color. Several times the camera angle changes and the debris appears and disappears several times throughout the shot. Most notably a splinter of wood on his shoulder.
Other mistake: After the final battle, the protagonists simply leave the scene and the remains of the T-800 and Rev9 behind. Sarah should've known by now that letting even the smallest part of a Terminator to be fallen into bad/incompetent hands could lead to disastrous consequences for the future of mankind. Being obsessed and even paranoid about future and fate, it's very unlikely that she could just go away like that, calling it a day before destroying all the present time traits of the Legion.