In entry C01769 in KEGG ((S)-Acetoin):
the stereo bonds are drawn in such a way that the intended configuration cannot be inferred (not by a human chemist, let alone by a computer program). The validation program gives an "ambiguous sp³ stereocenter" message. The name clearly indicates that it should be the (S)-isomer.
Entry MC001607 in BioMeta is now provided with correctly drawn stereochemistry: