In his intro, Boris Karloff completely mispronounced "os" (bones in French) which is pronounced "Ohss".
The bald guy says to Madalena "mon cher" which is masculine and is a grammatically incorrect way to address a woman in French. Even in Canada, the proper way is to say "ma chère".
A close up on the headmaster portrait in a wreath reads "En mémoire de". This is incorrect in proper French, and is not understandable in Paris, where this story takes place. In French, "en mémoire" is utilized in the sense of "commit something to memory". "In memory of" is "a la mémoire de", or even "en souvenir de". What is written is an Americanism, which is wrong in Fench but utilized in places where they speak "bastardized" French, such as Quebec.
When Madalena gets on the phone and talks in French 30 mins in, her French is heavily accented. In fact, she is supposed to be French but---more often than not---she rolls her R's when speaking English, instead of trilling them or sounding the guttural French R's. Towards the end, she even pronounces French words with an American "R". Luciana Paluzzi was Italian, not French.