There must be something different about the .ps1 filetype in the registry compared to the others.
If you go to Settings > File Types in Opus, then at the top File > Diagnostic, you can make snapshots of the relevant registry data for two types to compare them. Post them here and we can take a look.
You can also make Opus buttons, hotkeys or menu items to create specific file types: How to Create New/Empty Files
A diagnostic of the .ac3 file type might reveal what's wrong there.