Character mistake: One character says a concentration of 0.09 parts per million in the water is bad: "if it were salt it'd taste like you were drowning in the ocean." Rubbish. The concentration of salt in seawater is about 35,000 parts per million.
Factual error: Dick identifies a vehicle using licence plate. Problem is Michigan does not have front licence plates. (00:24:14)
Factual error: When Starfire gets out of the totalled car, there is a road sign visible. It is a settlement exit sign, denoting the exit of Königsstetten and Zeiselmauer as next settlement ahead. Obviously the makers tried to be extra thorough nailing down their "outside Vienna" location. They started OK - both Königsstetten and Zeiselmauer actually ARE outside Vienna - but then they completely botched it: Not only did they use a German black-on-yellow "StVO Zeichen 331" instead of the Austrian "StVO Hinweiszeichen 17b" which has black writing on a white base with a blue rim and doesn't list the next settlement, but they also put 852km as the distance to the next settlement, which is more than the length of Austria west to east. The real distance is 3.8km.
Continuity mistake: Gar enters a room and leaves the door open. Throughout the whole mirror scene the door is also open both when the camera looks at him and when the camera points at the mirror. However, when he is about to leave the room he needs to open the door as it has been closed inbetween us looking at Gar in the mirror and looking at him normally. (00:17:50 - 00:18:35)
Other mistake: After Starfire burns the guy in the room everything is burned but the picture, magically.
Other mistake: At the airport, after Deathstroke shoots his rifle, Garth (Aqualad) reacts to hearing the shot, turns around, and is then hit by the bullet. However, the bullet is traveling faster than sound and should have hit Garth (or Donna) before he heard the shot.
Continuity mistake: When playing Monopoly, Nuclear Biff rolls double 6. In the next shot, the dice change position. You can also see a 1 showing on one of the dice indicating the top number is not a 6 (it's a 2).
Other mistake: Conner's T-shirt never gets a bullet hole in it despite being shot in the chest. For example, we see him block 3 bullets with his body when saving Mr. Luthor. Nothing of his powers suggest he's generating a force field.
Continuity mistake: When Greyson is using the rental scan on his tablet, he's sitting straight up. In the next shot, he's bent over as he leans in to start the scan, but then he's back to sitting straight up. He switches position based on the camera angle.
Revealing mistake: When the assistant gets thrown into the wall by the brain controlled Gar-tiger, there are already marks on the point of impact, from previous takes.
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.
Continuity mistake: While Dick and Jason are talking the sun on the table is changing.
Bruce Wayne - S2-E7
Character mistake: After Jason falls from the skyscraper and is saved by Conner, he suffers some sort of PTSD. It is very hard to believe that a guy who fights crime all the time and fights people wanting to kill him so often (which includes Deathstroke beating and stabbing him like it was nothing) magically starts to suffer from PTSD just because he almost fell from a building. It doesn't make sense and feels forced.
Suggested correction: There was a lot more to the storyline than "some sort of PTSD." Of course, that kind of psychological trauma often doesn't make sense. Why would one veteran experience it and not another soldier who experienced the same thing. And he didn't "almost fell", he did fall off the building. If Conner wasn't there, he probably wouldn't have survived. He had never experienced failure in that manner either.
Bruce Wayne - S2-E7
Other mistake: Dick shoots into the bathtub to scare information out of the guy taking a bath. Three shots splash up - trouble is from the angle he was shooting at, very shallow, those bullets would have smashed through the other side of the bath, but nothing happens.