Audio problem: In the film left behind by the killers, the two men in the picture can be heard talking - but their lips aren't moving.
Visible crew/equipment: When Danno pulls up to the beach house, several light panels are visible, reflected on the surface of his car door.
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.