Article is from 2016. It is a good article, but why does it say OAEP is notoriously difficult to implement? OAEP seemed very natural to me, and I "invented" i

Article is from 2016. It is a good article, but why does it say OAEP is notoriously difficult to implement? OAEP seemed very natural to me, and I "invented" it myself (long after it was well known to others, of course), i.e. the ideas in it weren't complicated. Am I missing something dumb? I do remember hearing that Victor Shoup found some kind of bug in the security proof, but it wasn't something of practical concern.