Associate
This one : https://forums.overclockers.co.uk/threads/lg-38gl950g-3840x1600-g-sync-144hz.18840788/page-60 (first post page 60)
or this one : https://www.reddit.com/r/ultrawidemasterrace/comments/dfkpdr/lg_34gk950fb_wake_from_sleep_problem/
I have the same :-/
Fingers cross they will find the cause and hopefully fix it via a firmware update. Must be annoying sometimes.
I am sure I could live with it if I had this monitor but it would have to be a lot cheaper though.