The glass from which Dr Jekyll drinks the potion during the first transformation changes in size from tall to short between shots.
After the first transformation scene when Hyde attempts to change back into Jekyll, as he throws himself onto the floor, you can see one of his prosthetic fingers fly off.
When Jekyll is pondering to drink the potion for the first time, we see the glass he's to drink from is half filled with potion.
In the next shot when Jekyll brings the glass up to his lips the glass is empty.
When the giant spider apparition (manifestation of Hyde) climbs onto Jekyll's bed, the legs of the actor manipulating the costume are clearly visible.
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