My 'sync clipboard' has been off since before I started experiencing this problem (just double checked when I read your post). Glad it seems to be helping others though!
I've noticed that if I don't run any code, I can copy/paste as much as I would like. Once I run code, I start to have issues with freezing. I agree with poster @z_jackson that generally the longer I am using SAS, the worse the problem becomes.