When reddit is trying to access b.thumbs.redditmedia.com, it causes one of the firefox tasksin the task manager to use 100% CPU. This causes a freeze until this one task is killed. I am using the latest Firefox version 64bit. And also RES.
ghostery, adblock origin, disconnect, no coin, smart https. Thats all. It also only happens after idling for a longer time e.g. using another tab and suddenly the freeze starts.