Continuity mistake: In the beginning, when Michael Berg is sick on the street in Neustadt and is leaning on a wall to throw up, he's near a closed door and is positioned to the right of that door. Next shot, from inside, shows the door now open and he is leaning to the left part of the door. (00:03:15)
Character mistake: During the seminar, Professor Rohl tells students that only 19 workers of Auschwitz were sentenced (in 1966). During the first trial of Nazis from Auschwitz, 39 were sentenced, including 23 persons condemned to death. The trial was in 1947 in Krakow.
Visible crew/equipment: When Michael is on the train you can see a crew member's face reflected on the glass window of the train.
Factual error: In the streetcar scene a passenger is a soldier wearing a US Army green uniform with a CIB, Comat Infantry Badge. At the time US uniforms were brown and there is no plausible reason for this US soldier to be in that country.
Continuity mistake: When Michael comes back with a bunch of flowers, Hannah is ironing. One second she's ironing a girdle (I think it is), and the next second she's ironing a bra.
Continuity mistake: As Michael stands, naked, facing the bath, Hannah stands behind him, naked also and with a towel, to dry him; all through this, water has continued to fill the bath, but, miraculously, it turns itself off.
Answer: Those weren't scars. They were very superficial marks like she'd scratched her back.