The clock on the bomb wired to Billy Madrid's car shows the timer at 12 o'clock. When it cuts back to the bomb, the timer is at 5 minutes to 12. When it cuts back a third time, the timer says 12 o'clock again.
When Billy and Madeline are driving prior to the car bomb explosion, the sunlight changes from initially a high overhead, to a lower angle such as early sundown, then when the uniform police officer stops them, it changes back to high overhead.
When Officer Wells forces Kum Chi's two thugs off the road, she is driving the Mercury Marquis. Just before the thugs' car rolls, there is a brief shot of the old Mercury Park Lane. The next shot shows the Marquis coming to a stop.
When the goons' car is forced off the road by Officer Wells, it hits a parked vehicle and overturns, fortuitously missing the owner (he's standing on the passenger side). By the time Wells and McGarrett have pulled the dazed criminals out of the wreck, the innocent bystander has vanished, although his car (no doubt heavily damaged) is still visible.
Near the beginning, when the sniper stops shooting, before running away, he clearly lays the rifle on top of the air duct such that it's visible from the ground viewpoint. But when Danny and Chin get to the roof and find the rifle, it's laying beside the duct, down on the roof surface.