origin of gaps in navmesh of landscape

[barbrian0723]

hi
this is a snapshot of my terrain showing the navmesh
on the actual terrain itself, not the objects in the landscape, there are gaps which i did not plan to be there
can anyone tell my why those gaps are there?
it may be based on the geometry of the landscape perhaps
how do i test / affirm the origin thereof and how do i get it away?

thanks

[barbrian0723]

solved this with fill collision under landscape for navmesh