Trying to bake navmesh for skyscraper crashes Unity. Any ideas?

I'm making a level with a tall building (30-50 floors) and I've created a low poly piece of geometry that includes the general floor and stairwells. I'm baking my navmesh using this simple geometry. When I try to bake the navmesh "exporting tiles" hangs for awhile before crashing Unity entirely or giving me the following error message: "could not triangulate contours." The aggravating part is that I can bake a half dozen or so fine together, but anymore and it fails.

I'm looking for solutions or alternatives for getting agents to navigate a multi-floor building.

Thanks!