Shadows disappear

Can someone have a look at this gif and give their opinion of what might be happening please?

As can be seen (hopefully, I've never used gfycat before), at certain distances the shadows disappear on each cascade range. It looks as though it stops rendering the shadow map, but all distances that I can think of that could affect this are high enough to not be the cause - camera render distance, shadow distance in volume, cascade distances in volume.

I have a very basic HDRP setup for this scene. I've just added HDRP, Probuilder and progrids packages. There is a global volume in the scene using the DefaultSettingsVolumeProfile. No baking of shadows, only realtime. One directional light set to realtime only. Changing normal bias and slope-scale depth bias make only slight changes to the shadows and don't affect the culling.

The problem also changes when adjusting the scene view size as can be seen at the end of the gif.

The mesh that is casting the shadow is made in Probuilder. The only thing strange about it is that it is very large (80 units high) but with very few vertices/triangles. Think 1980s 3d model from the 'FreeScape' games. I don't know if that might make a difference, but it's the only thing odd about it.

Very strange. I can't figure out a workaround or what could be happening so would be very interested to hear what could be the cause. Thanks

 

For anyone else that might run into the same problem - update unity.

Was using 2019.x.x but 2020.3.2f1 has updates to HDRP apparently. Works fine with latest package (10.4.0)