When Jeff drives up to the cabin to meet Kathie, not only does he say it's getting dark but as he turns off the main road into the forest, headlights are shining on Kathie. But minutes later, after Fisher is dead, Kathie leaves with the car and there are no headlights on to guide her through a supposedly-dark forest. In actuality, it was probably filmed in daylight then filtered to look dark, but someone forgot to show the headlights that were needed in the false evening.
The goof item below may give away important plot points.
When Jeff Bailey, aka Jeff Markham (Robert Mitchum) almost gets killed in the mountains near the river while fishing, he has long hair. In the rest of film he has short hair. Mitchum was wearing his hair "long" (by 1940s standards), having come straight from the noir western Pursued, and was told by Jacques Tourneur to find a barber. Bridgeport didn't have one, and ultimately Mitchum drove two hours and 78 miles before he found one. This scene near the river in the mountains must have been recorded before Mitchum found the barber. Also the crew had delays during the mountain shoots (due to bad weather).
The Kid (Dickie Moore) pulls Joe (Paul Valentine) off a cliff by setting a fish hook into his coat and pulling him off to the stream below the cliff. But when The Kid and Jeff (Robert Mitchum) run up to Joe and leave his body in the stream, The Kid's fishing line is reeled-in with the lure and hook hanging off the end of the rod. The barbed hook should have still been thoroughly imbedded in Joe's coat.