Plugged in a tablet with SD card, navigated to the card folder, it was populated as normal but when I entered any folder they showed up empty. I unplugged the tablet and went through the same procedure, same results.
Left it plugged in and launched Total Commander, navigated to the same folders they were populated as normal.
So I closed down dopus and relaunched and everything was working as normal.
Just thought I'd let you know about this, a minor bug and I know now what to do if it happens again.
Most likely you had filters applying which were hiding things in the window you were using, or something was up with the card.
The directory listing comes from the operating system, so if it was inconsistent for any other reason then something is very wrong outside of Opus.