Always clearing the cache shouldn't be necessary and can be a problem:
viewtopic.php?f=3&t=1996

What exactly do you get or don't get? What behaviour do you observe? Do you have logs?

OpenSubtitles caches are limited to ~18 hours, so if you repeatedly search for the same thing, the data will be fresh the first time around, and guaranteed less than a day old on subsequent requests. That's pretty reasonable.