When becker is in the diner he flicks his match to put it out but in the next scene it is lit again.
Becker states that whenever he encounters a "short person" (meaning a dwarf), he always has bad luck. It has already been established that Becker has rejected religion as illogical, so embracing a superstition would also be.
Becker mentions having had ptomaine poisoning; as a physician he should know that ptomaine poisoning was discredited as a medical myth by the end of the 19th century.