My recollection of Kegworth was that a smell of burning on -200 and -300 737s was an indication of a failure on the side the flight deck air was fed from..
On a 737-400 they had swapped sides that fed the FD, which led to an immediate wrong conclusion as to which side engine had failed and a strong confirmation bias even when faced with the vibration indicator.
What similar issue could have affected the accident aircraft this time ?