I just posted up a clear cache bug in the bugtracker that I have noticed wasn't working. This happens when you hit the check box in certain pages and the page does a POST method instead of GET. So it may say it's clearing but it really doesn't.
Here's the bug fix if anyone wants to temporarily fix it.
Line 57 cache-images.php
old: if (isset($_GET['clear'])) {
new: if (isset($_GET['clear']) || isset($_POST['clear'])) {
Comments
So the cache of course is never empty afterwards. Simply checking it and hitting save for example won't do nothing.
Just to be sure I understand you right, because it is working as supposed in the latest nightly build. Maybe the checkbox is not placed to make that relation clear.
I will add you fix.