In the train scene early on Forrest Tucker is reading a fresh, crisp, unwrinkled newspaper when Janet Munro has one of her bad spells and falls in his lap. As she falls, Tucker's newspaper looks like it has gone through a few takes already.
When Alan is going to try out the Molotov cocktail on the monsters, he tells everyone in the hallway to move to the far end, except for one older gent with a black jacket, hat and mustache. He tells him to close the door after he gets outside. Apparently the man has trouble closing the heavy door because a balding crew member wearing a white shirt closes the door after Alan.
Trollenberg isn't in Switzerland nor in the Alps. The travel posters in the Trollenberg train station depict the Matterhorn probably as seen from Zermatt, Switzerland. Trollenberg however is actually located in Germany's Black Forest nearly 400 KM away. The closest rail station access to Trollenberg is in Loßburg about 4 KM away. Zermatt, however in the shadow of the Matterhorn, does have a train station and cable gondola service to Furi and Schwarzsee.
In the lab Prof. Crevett states the walls are steel reinforced. Yet when the monster breaks through the office wall where Anne Pilgrim is, there is obviously no reinforcement in the wall or in the piece of fallen wall shown.