Near the end of the show when Rockford is being chased, he hurriedly puts his briefcase into the elevator and doesn't punch any floor buttons. This means the elevator car would not have gone anywhere (it was after hours so no one else would be using it). If someone had just punched the outside elevator button the elevator doors would have opened and the briefcase would have been right there.
When Rockford looks up the address for Carson and Carroll, the close-up on the phone book clearly shows the address as 10001 Ave of the Stars. But when he gets there to clean the carpets, the address is stated as 6410 Spencer Street.
At the end of the episode, when Rocky's cutting Angel's hair, Jim complains he's 'tapped out' (of money). He shouldn't be - he should be ahead, by $4400 - the amount the 'Jones Bros' sent to him, in cash, in exchange for the marked money being returned. The $4400 was dropped in a mail chute, and sent by USPS, and therefore, wasn't in any way stopped from reaching Jim.
The floor machine that Mr. Rockford brings in to supposedly clean Carson and Carroll's office is obviously not on; not only is the handle not being held down (necessary for the motor to run), but if it were on, the machine would simply spin around, since the machine has a rotary action. The sound of it running was dubbed in.
The goof item below may give away important plot points.
At the end of the episode, when Dennis Becker (Joe Santos) is asked what Electric Larry (Roger E. Mosely) and his cohorts should be charged with, Becker reels off several provisions of the California Penal Code, including "attempted 287." He apparently meant "attempted 187," which would mean "attempted murder," because Electric Larry was about to kill Jim Rockford when Becker and the other police arrested him. Penal Code section 187 is the California statute for murder and several lesser offenses, but there is no section 287, nor was there in 1977 when this episode was made.