And one more thing to try out: Please go to Edit > Preferences, choose the Play tab and scroll all the way down, unfold the Advanced Options and there toggle the ASIO-Guard option, close and restart Dorico. Does it become better or worse?
no you didnt
enable asio-guard is already selected
Then toggle it please and see if it makes a difference.
the result is about the same
Strange, very strange your case.
Now, please get LatencyMon and let it run for a few minutes. Then do a second run, that time with Dorico in parallel.