iOS Build - Static Lighting - What setting causes this?

Does anyone know what causes the following effect? It looks as though the engine is calculating the lighting correctly and then applying a limitation that causes this strange effect? (reminds me of the cut-out filter from Photoshop). I’m looking to achieve smoother lighting as oppose to this segmented thing that’s going on. Compress lightmaps is already switched off.

This is a static spotlight and looks like this when deployed to an iPad. Lightmaps are clean and a suitable size (using 512 for this relatively small mesh).

Solved. Switching from PVRTC compression to ATSC compression in Project Settings- iOS immediately fixed this.