Wow! Thank you so so much for this comment. Finally I can sleep again tonight! I found nothing specific about this in the internet. I searched for hours. Now I can sit and relax until they release the Update. It looks like it's fixed there, because I'm not the only one with this problem. Also, apart from the 100 random wakes from sleep, every time the focus changes it wakes from sleep. Disabling Power Nap is a small workaround here, but obviously it's still randomly waking up from sleep, causing the monitor to turn on. Btw I have the MacBook Pro 15-inch 2018, so it looks like everyone could have this issue.