Jane sounds shocked that people use the word password as their actual password. In S4 E2, a victim has password protected files and Korsak keeps telling Frost to try 'password.' When Korsak suggests it both Jane and Frost dismiss the idea, but when Nina mentions it, Jane sounds like she's never heard it before and is surprised that people do it.
The flusher on the toilet tank did not cause the crack on the toilet lid.
Although the killer at the beginning is supposed to be female, up close it is indeed a male.