"generated inconsistent result for asset" warning

What is this warning and how to fix? 2020.3.0 LTS

Importer(MonoImporter) generated inconsistent result for
asset(guid:be8d835bbd9194c4686ca124ce0675ce) "....cs"

Execute menu command Assets → Reimport All.

From release notes:
“Unity version no longer written to serialized artifact files generated during asset importing. This was causing inconsistency import result across Unity versions. For existing projects, you must either do a “Reimport All” or delete the library folder for this fix to take effect.”

See also Issue Tracker page.