When Vollmer first walks to Ernst's apartment he removes his shoulder harness twice.
In the opening scene, Peter Vollmer is hit with produce of some sort in the face which splatters visibly along the left side of his head, hair, neck and left shoulder part of his shirt. He has no residue at all on any of those areas after he briefly fights with the heckler immediately after getting hit by the vegetable. Shortly later, when he returns home after the brief fight, the opposite side of his shirt (the right side which did not get splattered) has several spots evenly spread over that side...more spots than he could have gotten by falling in the street during his brief fight.
When Curt Conway stands next to the picture of the actual Hitler, it's very clear there isn't much of a resemblance.
Whilst the identity of Vollmer's mentor was probably sufficiently obscured by shadows to confound viewers at the time it aired, it's much more evident in the current Blu-ray pressings.
While Vollmer is demanding to know the identity of the man in the shadows, he accidentally knocks a microphone from his podium to the floor but continues to record the take.