You think the problem is with the software? What arrogance. The problem is that you have absolutely no understanding of what you're doing. You are very lazily crawling towards something, propelled by the charity of those who have actually done the work to understand this subject. I for one am done spoon feeding you after this. Now, consider the following scenario:
Just past the edge of your tile, there is a vertical wall which is too tall to jump over. The wall runs parallel to the tile border. As you know, your agent has a radius value. Let's say the radius is 1.0. This means that the closest your agent can get to that wall is 1.0 units. Given this information, your tile should have a solid line 1.0 away from the border marking the space as non-navigable. Or, put into visual terms:
To summarize, you need to provide some geometry beyond the edge of the tile you're generating, because it will affect the navigability of the edge of your tile. Here are two posts I found easily by searching which have already made this point (in other words, in addition to RTFM you should try searching, and then try learning this yourself):
http://www.ownedcore.com/forums/worl...ml#post2012008 ([Tool] Navmesh Creator)
http://www.ownedcore.com/forums/worl...ml#post2022402
I'm done with you.