Hi inv,
This issue should be fixed now:
What's new in Switchres v0.017l (November 2018)
- Fix issue where 4K pixel clocks caused an overflow in the modeline engine. Now Switchres can properly pick 4K video modes. However, AMD drivers will still reject custom 4K timings so, until this gets fixed, use the -nomodeline_generation in GroovyMAME when running on 4K monitors.