I have looked a bit into that what you have mentioned and this happens in the recast tool
aswell .it seems to be the result of the current pathfind function implimented which is called
straightpath ,in case of a partial path found it sets the last point to the closest point found on the
last polygon and i have done some tests ,it only adds other points between the last point and previous if theres a reason to alter the direction ,theres also two other path finding functions
i have not implimented yet one of which uses steering ..
Currently i have altered the plugon as to alow for rebuilding navmesh
which wil allow loading new levels and build theire navmesh obviously