When Georgia Crawford first meets Dr. McKenzie at the shooting range, he turns to her in surprise, holding both his pistols in his hands. After a brief conversation, she asks him if he is going to draw on her, and after that we see both of his pistols back in his belt. Although we don't see his hands during the conversation, we see his upper arms which obviously don't make any kind of move as to put the guns back in the belt.
When Sam shoots the trunk in 1886, the hole is different than the hole in the trunk in 1986 in the auction.
Several times while Scott McKenzie is driving, the sound is of a car being shifted with a manual transmission, as denoted by the engine revs dropping between gears. However, in a few shots, it is clear that the car is an automatic as McKenzie is shifting from Park into Drive when taking off or from Drive into Park when parking.
Special effect not synced with action. When Dr. Cole is standing in the field holding the time device in his hand, you can clearly see his hand moving around and under the glass while the device remains fixed in position and does not move with his hand.
When Scotty first looks at the tintype image, it only shows the 3 bodies in coffins. The next time it is shown, his Army friend magnifies the image. It clearly includes the man in the background on the left side of the image.
When the professor visits the general to enhance the photos, the soldiers are wearing O.D. green fatigues. Set in 1986 the soldiers should be wearing woodland cammo uniforms.
Future time traveler Georgia Crawford disguises herself and tries to blend in in the old west of 1886 by wearing a cavalry dress uniform. Despite the fact that she looks obviously female and in 1886 it was far more probable to see an adorable little boy in the US army than a woman. In 1886 it was totally illegal to enlist a woman, so the only ones in the army would be those who could pass as men. And though a law of 1864 gave heavy penalties for enlisting boys under 16, it may have often been ignored. In one case, a man and his two sons enlisted as musicians in 1870 and the ages of the sons were recorded as 14 and 11 - the younger boy was actually 9 - so that recruiting officer was not afraid the ignore the lower age limit.
Although Dr. Joseph Cole uses the term gunslinger several times, its first known use was 1920, nearly 35 years later.
When looking up the song about the Star Handled Stranger, Dr McKenzie and his colleague comment that not many people could read back in those days (the late 19th century). In fact, literacy rates for white Americans were very high in the mid and late 19th century. At the time of the Civil War, somewhere around 90% of white men could read and write. Literacy rates on the frontier a generation later would have likely been somewhat lower but literacy for whites would have been the rule, not the exception.
When the police officer in the cruiser is calling out the registration plate of the stolen vehicle, he says: "Zebra S...". The actual plate reads "2S...".
When Professor McKenzie hangs 2 antique revolvers in a frame, he cocks the hammers. No collector would do that, because it would eventually stretch out the springs and break them.