In the scene where Makoto opens the science lab's door, the glass window of the door is opaque. When Makoto enters the laboratory, the glass window of the door is transparent.
In the scene of the teachers room, when Makoto hears a noise from the science lab, there is a shadow next to the doorknob of the door of the science lab. in a close shot, the shadow is on the doorknob.
Spoiler: During the time-stop sequence Chiaki laments that he will not be able to see the painting he has come to the past for because it is in restoration and he will not be around the next day when it is put on the wall. But Makoto knows that the picture is worked on by her aunt and so they could just go upstairs and take a look at it (they may find the door locked but the possibility is not even mentioned). Chiaki's last jump could not have erased that memory because Makoto's knowledge predates the event.