I’ve been struggling with this for quite some time on both 5.1 and 5.2. I searched every forum I could find and I swear I read the Virtual Shadow Map documentation page a half dozen times. I even tried setting r.Shadow.Virtual.MaxPhysicalPages=16384. Any higher than that would crash the edtior. So this week, I moved my project to 5.3 and “Voila!” the problem is gone.