About 90 minutes in, there's a scene where Woody and Ozark are playing outdoors to an audience of prison inmates. As the camera zooms out, we see the edge of what appears to be a sky-blue painted backdrop, then we see movie reflector boards, then we notice a man walking through -- not dressed in 30's clothes, seems like a crew member, perhaps an Assistant Director. In the foreground, also not in period dress, a man, perhaps a props person removes some leg irons from the back of a prisoner's seat.
Then the picture cuts to close up of Woody and Ozark, then back to a wide shot where we see reflector boards, crew standing around and in the background. Smack dab in the middle of the shot, there's a movie camera with full magazine.
Guthrie's singing partner on KFVD radio in Los Angeles was not named Memphis Sue. Her real name was Maxine Crissman, and she was known as "Lefty Lou," because she shared Guthrie's politics and was just as outspoken. In fact, Guthrie was never pressed to stop singing union-organizing songs; the station owner, Frank Burke, was a populist New Dealer who agreed with Guthrie. The reason Woody was fired was because after the Soviet Union signed a non-aggression pact with Nazi Germany in 1939, he started singing songs that, mirroring the Communist Party line, denounced the war as a capitalist fraud.
The movie shows a scene with signs marking the California-Arizona border, where there is a checkpoint set up to turn people away unless they can show $50 in cash. The entire California-Arizona border consists of the Colorado River. The scene is shot in the middle of the desert with no river in sight. However, since the river runs at a lower elevation than the surrounding terrain, it is entirely possible to be within a quarter-mile of the river and not see it.