The dat files are manualy saved after you commenced a succesfull build you may save it out all at once or only single tiles if you need...

After its saved you dont need to do a build(with build all tiles) you only need to init the build with build all tiles =0 and load the tiles from file , all after filling the built list .. I actualy have to work on
fixing it to use empty build lists..

Edit : on second thought controllable detour crowd agent as a player wil irradicate this problem and adding a function to keep any object on the navmesh surface would also work ..but thats for another time


I may be wrong but i think your problem may
be that your caracter is standing off of the navmesh tiles because the border area on the edges do not go right up to the ledge it gets shrunk to accomidate the radius of max agent setting to keep paths away from obstructions so your agents cant get stuck ...so you may have the option of preventing your caracter from going off of the navmesh tiles border by using invisible walls or else find closest point on the navmesh from players position and use for target .. If you could upload i could look into it a bit more but cannot promise you much in the speed of my reply..thanks and good luck