Like Clint, I've got SEP 12.1.6, and I also noticed this issue right after upgrading to Win 10 version 1809.
The good news is that it looks like SEP is still functional. The Event Viewer is just going to get clogged up with these messages, but it's more of a nuisance than anything else. (There were previous versions of Win 10 where certain versions of SEP would not function at all, but that doesn't seem to be the case here.)