There are camera examples in the how do I FAQ (section scrolling/camera).
What do you mean by "it doesn't always position the person properly" ?
The only "bug" I noticed was that when falling from a platform, the character did not went back to the "idle" animation.
I'm pretty sure it has more to see with a little mistake in your complex code than anything to do with full screen, since it happens again even if I set the full screen to off.
It looks like your character should be clutched to a platform but instead is falling. I can press the "up" key when touching the ground (while staying in "falling" animation) and I get a "push up" like when I'm clinging to the platform and want to go up.