Oh man thats not good to hear.
Game Development is a long and sometimes frustrating thing. But never let it get you down!
Your awesome ideas has to be published, no matter the costs.
So since my idea did not help, and we maybe discovered the main cause of that issue:
Just copy your complete project into a 2nd folder so that your changes does not effect the main project.
After that, open the copied project and try to remove the navmesh blocking volumes.
I want to make sure that this is really the issue.
If so, try to get a workaround, or check the settings of the navmesh, disable any effect on the world you dont need with that.
Good luck!