Did you get the problem fixed? I've got the same problem and its actually enough of an issue to need to get a new phone.
How have they not fixed this and sent out an update??!!?!
This is astonishingly bad response from Samsung on here.
I purchased the S9 yesterday and am seeing this problem. Already I have missed some imprortant family information, to which I have notifications muted as when I work I prefer not to have the phone going off constantly, but when I unlock I should be able to see if there are messages waiting for me.
I require a response now. I work in the technology industry and this is simply not good enough