This issue has been around since at least January 2016, if not before. It happens in Google Chrome & Safari. CCleaner does not clean out some or all of the cookies & history. In some cases it will stall while attempting to clean Google Chrome. I was in touch with Piriform about this in February, & this is what they said:
"Our development team has confirmed that CCleaner stalls when cleaning certain Google Chrome files, just as you've reported, and they are currently working towards fixing this problem. We expect this to be resolved in the next version of the application - v1.13. We also noticed that CCleaner is not cleaning the Channel ID cookies from Chrome, as you have also reported, and this is due to a recent update of the browser. We'll also try to get this fixed in the next version of the product so that these cookies will be removed as well."
It's 2 months since I received this info, & still no fix. Shame on Piriform for not fixing this in a timely fashion. Many people will be using this program & not even realize that it's not working as advertised. (No error messages are generated, in fact CCleaner will report what has been cleaned when in fact it has not been cleaned) I consider this to be a real privacy & security issue, that many users will not even be aware of.