When Jim leaves Slauson's office building at 2520 West Olive Ave., he turns around and heads west on Olive Ave. When the goons in the Mercury are seen following him in the long shot of both cars, he is traveling east on Olive Ave right in front of Slauson's office again.
At Karen's place, Rockford's line of "...so let's stop with the flickering candlelight and romance angle..." is muffed - Garner mispronounced it as "angel".
When Susan Strasberg's character is leaving the tennis court, she's not wearing tennis shoes, but white casual shoes with a pretty steep heel. This was done to make up for her and James Garner's significant height difference as they converse, but nobody plays tennis in heels.