Multimonitor Setup with different refresh rates does not work with 360 Hz + 60 Hz (but 300Hz+60Hz does)

I’m using a 60 Hz FHD screen via HDMI plus a Dell Alienware AW2521H 360 Hz FHD via DisplayPort on my Sapphire RX580 Nitro+ 4GB. I can only use both displays simultaneously if I reduce the refresh rate for the Dell screen to 300 Hz. With 360 Hz I can only use a single screen, the other remains black. Manjaro is up-to-date and I am using gnome and X11.

What could causing the limitation? Thank you very much in advance. :slight_smile: