Is there a way to correct Navmeshing in Settlements with Existing Savegame's?

[Thirdstorm]

So goggle has failed me..

 

I've created a huge multi-story circular tower and found out the overlapping floortiles, even set at different levels (0.5 to avoid display issues) causes the settlers to completely loose their minds (flickering in circles as they try to navigate the structure).

 

Is there a way to force override Navnmeshing?

Is there a way to go into the save and force the Navmeshing?