Just before Katie's one-night stand with the billiards player, the man playing pool is lining up a shot using the cue ball, like normal. When the camera re-focuses on him, he's now using the 9-ball.
When Lucy speaks for the first time, her hair is relaxed - an irreversible change to straighten natural Afro hair- but before and after this she has the same natural hair. Which is impossible given the time span.
At 1:42:35 when Katie gets out of the bath and is sitting on the edge of her bed, she has on a black bra. She gets dressed and is then shown running. Her white bra strap is visible due to the movement of her shirt.
After Katie goes on her run with Cameron, there is an aerial view of Manhattan including the Twin Towers. Her mother died around 1989-1990 per the first scene, and we are now supposed to be seeing her 27 years later, which is well after the towers were no longer standing.