x5000 - radeon RX550 - 3840x1600x60 not working

hi.

i now have a RX550 in my x5000. nice card!
but i still miss how to use full resolution on my eizo monitor.
this would be 3840x1600x60hz. and this does not work,
it is listed in the screenmode prefs but the mode mode does not even work. when testing it screen goes black and even goes to sleep.
wakes up again after test is done.
using 30hz is fine. but really not usable. i want the full 60hz.
RX550 should be capable to handle this. also the monitor of course. also the HDMI cable. tested with my son's windows machine.

checking the debug output of the rx driver when pressing the test button in screenmode prefs i can see:

Quote:

any idea?
using the latest RX driver (enhancer 2.2)

i wanted to create a bug report on amiga.org but after registering there i don't get the registration mail...

thanks and regards
michael