Continuity mistake: When Iris is showing Frost's mother the obituary, in a shot facing the mother she's holding the folder open, then after she says "it feels cold", the shot changes to behind her and the folder is instantly shut.
The Man in the Yellow Tie - S8-E18
Continuity mistake: At the start when Flash is struck by the accidental lightning, he rolls on the ground and gets mud on his back. When he stands up, and we see his back in a reverse shot, there's no mud.