Continuity mistake: When Anakin goes to pick up Obi-Wan after the fight with Count Dooku, the floor is completely different from the floor seen when Obi-Wan was lying unconscious earlier in the scene - the pattern and the colours are different. (00:12:45 - 00:14:35)
Continuity mistake: When Anakin, Obi-wan and Palpatine are running through the hall and get stuck in the ray shields, Anakin is facing forward. When it cuts he is suddenly facing Palpatine. (00:17:10)
Continuity mistake: When Grievous throws his staff on the window making it crack, the pattern on the cracks change between the shots. (00:19:50)
Continuity mistake: Yoda sends Darth Sidious flying over the table knocking down his chair. But when Darth Sidious jumps back over the table the chair is up again. (01:45:35)
Continuity mistake: When Obi-Wan and Yoda find the dead Jedi, some of the dead children lying on the floor where Obi-Wan and Yoda are standing are lying in a different position between shots. For example, watch the brown cloak of one of the Padawans near Obi-Wan. (01:30:40)
Continuity mistake: When Obi-Wan gets on the intercom with R2 the first time on Grievous' ship, as it cuts to R2 backing up against the corner hiding from the droids we can see that there is no light casting his shadow. When it cuts to R2 again two shots later, bright light suddenly appears, casting his shadow. (00:09:10)
Continuity mistake: When R2-D2 shows the hologram of Palpatine's whereabout in the spaceship, we can see R2-D2 is looking to the right. When it cuts to a wideshot he is looking to the left. (00:07:45)
Continuity mistake: In the first shot of the scene where the Jedi Council refuses to give Anakin the rank of Jedi Master, Obi-Wan has both feet on the floor. In the next shot, one leg is crossed over the other. (00:33:35)
Chosen answer: Powerful force users seem to have some degree of control over their bodies even after death. In the later series, Luke's wife Mara Jade Skywalker only allows her body to disappear when her killer, and nephew Jacen Solo arrives at her funeral as a clue. Thus it appears that a powerful force user can simply choose if they wish their body to disappear.
Darius Angel