Glenn's candy tin moves from his hands to his desk between camera angles.
The type of forklift seen here has a safety mechanism under the seat that will not allow it to turn on or be put into gear unless there is weight on the seat, like that from a human body. There would be no way the forklift could have driven off on its own without a person, or something of similar weight, in the driver's seat.
When the shelving in the back room is collapsing around Jonah and Amy, a piece of clear Plexiglas around the open back of the forklift, likely part of a safety measure to protect the stunt actors, can be seen wobbling.
When Dina confronts the shopper buying a condolence card, one of the questions she asks is "Vegetarian or normal?" Dina is a vegan, and wouldn't say something like that.