The character Roy is listed as "Lloyd" in the closing credits.
When Jerry asks Kramer, "Did he say anything?" in the final scene, Jerry's left hand is empty. In the next shot he's holding a blue container.
George unbuttons his pants when lying on his stomach for the massage, but when the masseur asks him to take them off, his pants are buttoned again.
When Kramer starts to bang on the table and yelp, Julia Louis-Dreyfus can be seen breaking character by laughing and looking at the camera.
The mere existence of duplicate referrals for Elaine would not cause any problem; the question of fraud would only arise if both notes were turned in to the clinic and then into the insurance company, and why would Jerry give them the one he got from Roy? He would give Elaine the note for her to hand in.