Factual error: Tom Keene watches an arms deal. The supposedly German plates of the BMW read "DD17-36F9." This, however, is not a possible combination in Germany, as there would not be numbers in the first half, nor a letter after a number in the second part. [exceptions from the first being the most important officials' cars like the federal president's, but even then the latter applies.]. Furthermore, no more than 4 numbers can be used, except for in police and military vehicles (which also never have a letter after a number, and start "Y" for military, or "DD-Q" for Dresden police). "DD-F1736" would have been a correct plate for the town of Dresden, for example.
Revealing mistake: When turning the guy with C4 around his neck, the 4 person safe box window shakes briefly. If this was a bomb proof safe box, the glass would be at least 1.5"+ in thickness and would not shake simply from some walking. That box would be shrapnel to a C4 bomb inside.
Continuity mistake: When Keen enters Red's Bethesda apartment, the camera pans over pictures on the mantel. Directly left of the picture of a little girl/man on a swing, is a picture of a woman holding hands with 2 children (looks like 1980's, adult woman looks like Keen.) When Keen reaches out to pickup/view the swing picture, the woman/children picture is no longer there and a really old family photo is in its place.
Other mistake: When Reddington is close to death and is saved by a lung/heart operation in his field hospital, minutes after the operation the site is attacked and Red is left trying to defend himself from gunmen. Not only does he find the strength to pull out all the monitor wires and lines attached to him, but when he goes into the corridor to get a gun, he is fully dressed in jacket and trousers (pants). Did the very efficient hospital team forget to bring a hospital gown for him to wear? Did they operate on him while he was wearing his street clothes?
Factual error: The episode starts with a scene of a household in Koidu, Sierra Leone where a family is killed and boy taken. Mombasa is an island town on the coast of Kenya, not Sierra Leone. Mombasa wouldn't have a village or poachers or wild animals because it is an urban area. And Red later on reveals that the boy who was taken after the family was killed was actually Dembe, whom he found tied up in a brothel in Nairobi, which would again place them in Kenya, not Sierra Leone. Dembe would be an appropriate name for a person from Sierra Leone, not Mombasa.