Second external screen stays blank with wayland but works with x11

I have a lenovo T14 (AMD) that I connect via a thinkpad usb-c dock to two external displays (iiyama 2560x1440). The dock acts as a MST hub to drive the 2 displays. Under x11 I had to lower the refresh rate of the displays to 60Hz to lower used bandwidth to make both external displays work at full resolution.
Now I wanted to switch to wayland (because of better scaling support) but under wayland only one display gets a signal on full resolution (even when setting the refresh rate to 60Hz). Both displays are shown in the system settings display configuration (KDE plasma) but the second one only gets a display when I lower the resolution of one display to 1920x1080. Even when I switch back to x11 (log out and start kde with an x11 session again) the display stays blank and I have to reboot to make it work again in x11.
Is wayland using more bandwidth than x11? any suggestions what I can try to make both displays work with wayland? My workaround is to use the hdmi port on the notebook itself so I don’t have to rely on MST but that kinda defeats to purpose of my dock…
I am not too versed about display settings and desktop environments in linux, so if you can give me any hint what I could try, I’d appreciate it.

KDE Plasma Version: 5.27.4
KDE Frameworks Version: 5.105.0
Qt Version: 5.15.9
Kernel Version: 6.1.30-1-MANJARO (64-bit)
Prozessor: 16 × AMD Ryzen 7 PRO 4750U with Radeon Graphics

That would also be my assumption. Note that wayland is usable, but not mature in every aspect on any DE. Therefore, I would suggest filing a bug report:—