...And I Want Some Candy and a Gun That Shoots - S4-E6
Continuity mistake: Danno boards the helicopter wearing a brown suit, but arrives wearing a Hawaiian shirt. When he gets out of the aircraft a few shots later, though, he's back in the brown suit, with no time to have changed.
While You're at It, Bring in the Moon - S4-E19
Continuity mistake: McGarrett approaches the Governor's office building wearing a light blue suit, but enters the lobby wearing a dark navy blue one. (00:27:05)
Continuity mistake: McGarrett leaves the parking lot driving a two-door Ford Mercury, but arrives at the crime scene in a newer, four-door model. (00:07:25)
Odd Man In - S4-E14
Continuity mistake: At the end, Filer puts his jacket on, and the left side of his shirt collar is sticking out above the coat. Every time the camera angle changes, though, the shirt collar is neatly tucked in. (00:49:00)
The Ninety-Second War (2) - S4-E17
Continuity mistake: When Vogler stands in the doorway talking to Danno, the position of his arms alternates with each change of shot, from down at his sides to propped at 90-degree angles on his hips. (00:42:05)
Answer: He was fired. He never really appreciated his character. He felt Kono was portrayed as a big dumb Hawaiian and that the stereotype was racist. He also felt underutilized. He was fired after a heated argument with the show's publicist regarding his character. It seems there's not much details given regarding the incident or the firing, so it's seems possible he upset the show's producers as well.
Bishop73
No he said something derogatory about one of the Jewish producers that's why he was fired.