The background view of the Washington Navy Yard still shows the USS Barry docked. The USS Barry (DD-933) was a Forrest-Sherman-class destroyer commissioned September 7, 1956, she served during the Cuban Missile Crisis and the Vietnam War. She was decommissioned on November 5, 1982 and turned into a museum ship in the Navy Yard, however due to the cost of maintaining such an old ship she was hauled away and scrapped on May 7, 2016.
At approximately 39:35, the same man twice walks up the stairs behind McGee while he's conversing with Nick.
The Copperhead that Knight and Winchester came across on the trail was a Broad Banded Copperhead that is found in Texas and Oklahoma. The Eastern Copperhead resides in Virginia.
While describing Rocky Mountain Elk, Gage Winchester called them Bucks and Does. Deer are Bucks and Does. Elk are Bulls and Cows.
Kasie used the computer to fill in gaps and construct composite fingerprints from various partials but spoke some nonsense about "pulling data from those in the system who fit the serial killer profile". Fingerprint patterns are merely shapes and people's profiles (criminal or otherwise) have no effect on what their fingerprints look like. She goes on to talk gibberish about "filling the gaps"with data about individuals around 6 ft tall, probably Caucasian male, known history of knives, etc. None of has any connection with fingerprints.
Palmer goes for lunch in the diner, in his scrubs. That is unprofessional. The clothes could pick up all sorts of contaminants and compromise any evidence he works on later.
Palmer said that his autopsy showed that the deceased's stomach contained some partially digested rib-eye steak. There is no way to tell what kind of steak it was from a visual examination, after it had been chewed and digested. Even biochemical analysis in the lab would struggle to tell.
Winchester says he hopped a "redeye" from Maine, Knight said "so you flew overnight to be here?" Flight time from Maine to DC is less than two hours, there are no "redeyes", no overnight flights and it is the same timezone.
Parker refers to the scarlet tanager as extremely rare. In fact, the population of these birds has been stable for decades and it spends spring and summer in the forests of the northeastern US and Canada, migrating to South America for the winter.
Given that Winchester was supposed to be confined to the NCIS building, it makes no sense for Parker to bring him along to the diner to arrest a suspect. His presence there would serve no purpose, other than as plot device to show him lose his temper with the suspect.