I had a 128 gb ScanDisk card in my first s9+ bút I smashed the screen and got a replacement phone. I had the error message with the first phone but no real issues though. When I put the card into the replacement phone it was fine for a while but one day the whole phone froze which was unusual as it never happened. I had to power it off and restart it. When it started the error message came up and baaaammmmm next day it didn't recognize my card anymore.
I changed it to a Samsung 64gb card a couple of days ago and no problems whatsoever yet.
Yep, totally agree, it's a great phone that I'm more than happy with.. Just a shame (major understatement) that Samsung haven't done anything about this when it is now affecting the S10 as well!