Frustum culled landscape components stop casting shadows resulting in the shadows disappearing near the edges of the camera in square sections.
Unable to test in 4.20 or 4.21 as provided project was created in 4.22
Found in 4.22 CL#5275346 and 4.23 CL# 5287285
Frustum culled landscape components wont cast a shadow
Shadows would still be
There's no existing public thread on this issue, so head over to AnswerHub just mention UE-71030 in the post.