When Pimento stamps the insurance claim form "DENIED", the stamp on the paper shows large gaps where the stamp did not contact the paper, but when he then holds the paper up, the stamp has no gaps.
When Amy is running down the alley, chasing the suspect, she flips over a cart. She (or the stunt person) is seen wearing knee pads.
When Amy is trying on a wedding dress, Rosa is sitting (in a mint bridesmaid dress) with her legs crossed. At one point, it cuts to a different angle and Rosa's legs are uncrossed and spread more than shoulder-width apart. The angle changes again and her legs are suddenly crossed again, only for her to uncross and spread them in a similar fashion when a call about a fleeing robber comes over the radio.
Captain Holt wears his Commendation breast bar above his World Trade Center Breast Bar. When the WTC bar is worn, it is worn above all other medals, but below the American Flag bar.
Santiago is wearing 2 citation bars that are not issued by the NYPD. Also, NYPD regulations require that the American Flag bar be worn as the highest citation bar - something Santiago would have known.
Captain Holt claims to not have a social media presence, specifically mentioning Twitter. In Pontiac Bandit (2014), he complained that Gina's live-tweeting ruined Downton Abbey (2010) for him, something that would not be possible were he not already on Twitter.
When sending his first tweet about the water main break, Captain Holt gives the time as 20:40 (or 8:40 pm). It is still midday.