This is well known issue of all shadow maps in all engines.
Simply speaking.. learn to live with it.
Yes you can tweak gsm vars, but this will trade for low range shadows, and/or low quality shadows on higher distances or strange transitions between lods. IMO is not worth it. I wasted 5h for tweaking this var, and ultimetly gone back to default settings ;p.
If you have DX11 graphics card, you look for GS something (geometry shader shadow generation), and see if using this will fix your problem. As those are variation of stencil shadows.