To add on to @brs-sebascova’s answer,
This could also be due to a physical page pool overflow- or when the number of cached pages exceeds the max page limit. You can use r.ShaderPrintEnable 1 and r.Shadow.Virtual.ShowStats 2 to debug and see if this is your problem. If it is, you will need to either decrease your number of shadow-casting lights, decrease the shadow resolution, or if you aren’t too worried about performance you can increase the maximum page pool size with the command r.Shadow.Virtual.MaxPhysicalPages