TG3 - Standalone does not show correct on 3860x2160

I use a screen with 3860x2160. When I use the standalone, the windows is a vertical rectangle. The upper half shows the piano plugin, the lower half is only a grey area. When I switch to 1920x1080, all is fine & shown correctly.

Comon people, nowadays a 3860x2160 resolution should be supported! No problems with halion or groove agent, but with The Grand 3 ?