Shadow bug for faces with negative Z coordinates?

Looking for a solution for a problem I’ve been struggling with.

Using 4.19, forward renderer enabled, no distance fields enabled.
Static Skylight (with HDR), stationary directional with cascaded shadow maps (1500 - 3), no far shadows.

For some reason, the shadows on the imported terrain mesh (static) are messed up beyond the shadow distance . When moving, the transition line (arrow in the image) between mess & nice cascaded shadow quality moves as well.

It only happens to faces that have negative z coordinates.
If the terrain is flattened (all z=0) and re-imported the shadow looks fine.
If the terrain mesh is moved so all Z coordinates are positive, the shadow looks fine.

Any ideas / suggestions?

Hello,

We’ve recently made a switch to a new bug reporting method using a more structured form. Please visit the link below for more details and report the issue using the new Bug Submission Form. Feel free to continue to use this thread for community discussion around the issue.

https://forums.unrealengine.com/unreal-engine/announcements-and-releases/1410408-unreal-engine-bug-submission-form

Thanks