Collisions and similar issues

A couple of points I noticed:

1. When setting up a character/animal and hitting play in Unity the AI object seems to float a small amount above the ground. Animation etc seems fine and I have checked it is not hte animation causing the issue. Almost like the colliders are pushing it a bit above the ground. (I have tried moving the sphere and box collider to no avail)

2. When chasing or approaching an AI I seem to randomly hit an invisible wall, or in extreme instances actually walk up into thin air above the AI. Is this related to the rigger radius somehow?

3. Lastly, I can walk through my AI. Are you planning on capsule colliders or can I add one easily? I had a go but didn't have much success.

Essentially it looks like there are issues around the colliders so some documentation on that would be useful.