PS reverts to Desktop when saving a file No matter what options I set

There is a preference checkbox to "save as to original folder". Unchecked, it goes to the last used folder.

If this doesn't work as advertised, try to reset preferences.

If it still doesn't work, that points to a permissions issue in your Windows user account.

I have a slight update to add. I reset options as per an old reply to something similar.

Now when I come to open a file The explorer box opens on the last folder I loaded a file from. But then quickly changes to the Desktop. its as if I quickly clicked on the desktop icon.