When Clare was listening to the audio record and getting very sentimental and cried, the screen was actually working but the audio was OFF.
When young Emily and her mother are driving through the countryside, the caption says "West Berlin, 1984". However, they arrive at Schloß Sacrow near Potsdam, which was in East Germany at the time, as was the nearby Heilandskirche, where she hides her mother's ring. Both buildings were inaccessible to the public before the Berlin Wall fell in 1989.
There is no possible way the bad guys could know that Moritz had the communicator allowing them to kill him and steal it. This kind of thing is done all the time for dramatization and is a ridiculous error.