CCleaner isn't cleaning 98% of files on my Mac

CCleaner for Mac
1

I've noticed this problem when I've used CCleaner a few times now - Analyzing my computer for cookies, etc. shows over 124 MB of unwanted files and other stuff (currently). After I click 'Clean' the CCleaner only cleans maybe 4 MB of stuff, leaving the rest untouched. Even after several tries, only a couple of MB are cleaned up each time.

I use a Macbook Pro with MAcOS Sierra 10.12.5. I should add that my browser is Firefox 54.0 and it is where most of the uncleaned files are coming from.

2

Similar thing happens on my iMac with a 1TB fusion drive. Since this is and SSD, the drive wipe feature does not work. However, I also can't delete the firefox internet cache files. I run the analyze, then clean, rerun analyze and there is no difference from before and after I do the clean (42 files, 14194KB). The application should at a minimum be able to clear the cache file.