I think I'm experiencing the same issue. It seems to be a problem with Renderer::calcCropMatrix.
I've got a test scene that is just a big box for a shadow receiver (with casting off) and several bush meshes lined up in a row. I've got a light with a 90 degree fov, radius of 13 and y of 2. Normally everything appears just fine:
But I've got a procedure that automatically combines all the meshes in a scene node into a single geometry:
If I combine all the bushes in to a single mesh the crop matrix gets cut strangely and the shadow maps become much more expensive:
If I move the combined mesh more towards the front or back of the light it starts to correct:
Rotating the light on any axis (y pictured) also causes the cut off to change:
Commenting out the call to Renderer::calcCropMatrix in Renderer::updateShadowMap "fixes" it. I've tried fiddling around with it, but I've had no luck. Adjusting the light's FOV and radius doesn't have any effect.