I get the standard Windows 'Save' or 'Save as' dialog window

Before the last update (12.21 x64) when I made a new document or changed a document and wanted to save it, the interface was the one of Directory Opus. With this new version of Directory Opus I get the standard Windows 'Save' or 'Save as' dialog window.
How to change this again to the behavior I want?

Opus has never replaced the standard Open/Save dialogs.

Yes, I read that too. But still it was working like that in my situation.

Opus can launch instead of Explorer when programs ask for a folder to be displayed. But it doesn't and never has replaced the dialogs for choosing a file. If that was happening, it must have been via something else.

There are tools which change how the File Open dialogs work, some of which interact with Opus in one way or another. Maybe you were using one of those?