Use "Test navmesh" on the Navmesh toolbar. Choose your actor in this window and click "Display overlay". You will see the possible pathing of your actor. If your space is very tight, use small triangle to make the navmesh on the path of your actor. You can also select every triangle you want your actor really use and mark them as "Prefered" with the P key, the prefered path will turn yellow. Also delete every triangle with static object on it, and create small triangle to go around every static object.
Also look if you don't have a yellow line somewhere in your navmesh, actor can't pass them.