Yeah, keeping the plate chiller clean and sanitary, which means free from any clogs, has been a bit of a challenge. There are many good ideas around to accomplish that.
There's only one rule:
Prevent any solids going down the chiller!
Cold and hot break by themselves have not posed any issues. Hop matter, (fruit) pulp, large grain bits, Irish Moss, etc. need to be contained. Hop bags and/or a filter before the exit port can do the job.
Once that's in place, cleaning and sanitizing just becomes routine as with anything else on the cold side.
Compared to plate chillers, counterflow chillers are just one fairly large passage that can handle quite a load of solids. The larger diameter the inner tube, the more and larger solids can flow through. When clogs occur, they can usually be blown or flushed out.