Revealing mistake: At the river to cross over to Mt Weather, the vine used to swing across the river is just a standard rope, camouflaged. You can see it best when Finn recovers it after Jasper has jumped.
Continuity mistake: During the fight between Anya and Clarke in front of the drop ship they are both covered in grime, and after Anya hits Clarke with the log Clarke's face becomes increasingly smeared with blood. Throughout the scene, you can see Clarke's face switch between grimy and bloodied at least a couple times, most noticeably in the shot just after Anya tackles her into the ground and the following one. (00:34:25)
