When the boat captain, Marlowe, and Malloy are negotiating about the boat rental fee, the captain's cigarette suddenly disappears between shots.
When Lindsay Marriott is in Marlowe's office, there is a baseball in front of him on the desk on the left side of an ashtray. But on the following cut, the baseball has changed orientation and is now on the right side of the ashtray.
When Georgie tells Marlowe he has found a boat, Georgie's left eye is bruised and swollen shut. Seconds later as Marlowe starts to board the boat the camera pans to Georgie's face and his left eye, although still bruised, is wide open with no signs of swelling.
When Marlowe heads to the newspaper stand, in his narration he says that Joe DiMaggio had just hit in 33 straight games. But the newspaper had the headline of Hitler invading Russia. This is historically incorrect. DiMaggio's 33rd straight game occurred on June 20, 1941, his 34th straight game occurred on June 21st, and his 35th straight game occurred on June 22nd. Germany invaded Russia on June 22 therefore DiMaggio had to at least hit in 34 or 35 straight games by then depending if the newspaper came out the same day of the invasion or the day after.
The story is told in July 1941, but the hooker is reading a Whiz Comics dated Oct. 31 (and is a real replica of the 1941 issue).
At about 17:20 the little boy, Andrew, runs up behind Robert Mitchum in the hallway. Instead of getting his attention by saying, "Mr. Marlowe", he says, "Mr. Mitchum". (Not a goof -- Andrew says "Mister, mister".)
When Marlowe (Robert Mitchum) drives up to Mrs. Grayle's home (Charlotte Rampling), the front entrance is obviously double doors but when the butler is shown opening it from the inside, it is clearly a single door.
At 0:15:45, Marlowe gives the flophouse night clerk an "Abraham Lincoln," i.e. a $5 bill for some information. The $5 bill, clearly shown to the camera, is of modern (c. 1975) issue, although this story is set in 1941.