When Bunny and Naina are boarding the train, Bunny picks up Naina's luggage along with her book. A second later we see him boarding the train while Naina is behind with her book still in hand.
In the song "Badtameez Dil", during the line "Aaj sare, Chaandh taare...", Aditi is holding her shoes in her hand but they suddenly jump onto her feet.
When Aditi is telling Avinash and Bunny to become friends again, her hair keeps changing between shots.
Kabir hears a part of Aditi's video message in one scene. But in the next scene, the video clip is shown playing from the beginning.
Towards the end of the movie, when Ranbir Kapoor is at the airport, the announcement says "Final boarding call for all passengers traveling on British Airways flight 138 to Paris". Assuming Ranbir is traveling from India, BA doesn't fly to Paris. BA 138 is the flight code for Mumbai to London flight.
In the Sangeet scene, Lara grabs glass of wine from Naina's hand and does not drink, wine is clearly shown falling.
In the Sangeet scene, Lara calls Bunny "Sunny".