Background on PNG thumbnails are black - not solved by new helperphp.php
I am noticing that my transparent backgrounds on my PNGs are not staying transparent as per the fix. I have replaced "HelperPHP.php" in the config folder as per the instructions and also renamed and replaced "helperphp.php" in the "webassist/file_manipulation/" folder on the site in question (and uploaded the file) **This was not mentioned in the hotfix readme notes BTW.
I get a transparent image on the main image, but all of my thumbnails have black backgrounds. Is this a known issue?