navigation and mechanim root motion.

So 2 issues here. First setting speed to 0 and having root motion does not allow movement have to put at least a token speed in like.01 etc is there a way round this.
And B with root motion my guy doesn't walk in a straight line but veers off a bit until halfway to target then veers back in a want him walking straight no veering as its a road how do i correct this.
Thx