Two glaring inconsistancies.
I truly love these classic old movies. But even I acknowledge the silly inconsistancies in these films.
In the first two films, the interior of castle Frankenstein shows late medieval architecture (rooms with multiple doors, many with brief flights of stairs going to slightly higher hallways) but in this one the interior is totally and bizarrely different. The walls are bleak and windowless and the flights of stairs are crudely and crookedly hammered together with rough wood.
Moreso, in the first two films Dr. Frankenstein's lab is in an old tower keep miles away from his castle. Yet in this film it is within walking distance of his home. And tho destroyed at the end of the second film the rubble formed the shape of a rough pyramid, which is the shape of Frankensteins destroyed lab in THIS film.
Yet, while his lab was on the top floor in the tower it's down now on the bottom floor, mostly intact.