Lilian Stanhope addresses Columbo inconsistently, pronouncing his rank as 'Loo- tenant', the American way, and 'Left-tenant' the British way. An English actress of her standing in the 1970s would always use the British pronunciation.
As Columbo sits reading the Evening Echo on a bench, an elderly man is feeding the birds next to him. His position changes noticeably over camera shot changes as O'Keefe walks over and attracts the Lieutenant's attention, from upright to leant over.
In the very first scene, Nicholas stops with his car in front of the theatre. There are road markings in the middle of the street in one shot. In the next shot they are gone. There's also a completely different set of people on the pavement/sidewalk.