Now I see what's happening. OPM detects that EncConv package dependency is already installed and does not download the latest version. So yeah, KodeZwerg evaluation is correct, you should uninstall EncConv too. Another solution is to check package EncConv, before installing ATSynEdit thus forcing OPM to download the latest EncConv.
PS: If you wondering why OPM cannot detect that envconv has changed, the reason is simple, no version information has changed in ATSynEdit or EncConv, so the MinMax package dependencies are met. OPM cannot check every pas/dfm file for changes, that would be an overkill.