Character controller slowing down on 3d terrain mesh exported from Blender

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:bust_in_silhouette: Asked By Ethan Shearer

Ha all,
I have created a first person character controller based on the bellow tutorial.

This has worked perfectly on a flat terrain I built in Blender, however now I have created some hills and slopes on the terrain now my character slows to a crawl. This happens as I move to certain coordinates (negative I believe) of the terrain whether I am on a flat surface or a hill. moving to other areas works as expected (same speed on hills and flat surfaces)

Am I exporting the mesh wrong? I anyone can help point me in the right direction I would appreciate it greatly! Thanks