GigaBuist
Three things:
First, when you take it apart, check the recoil spring guide rod to make sure it's straight. A lot of the time, when some monkey tries to reassembe the thing, and doesn't get the parts lined up properly, they just whack it good with a rubber mallet, and the rod will get bent.
Second, people have found 30-year-old cigarettes, wads of cloth, paper, photos, diaries... all kinds of things stuffed into the cocking tube. Century could try to clean them out before thye sell them, but that would add at least fifty cents to the cost of manufacture...
Totally strip it down and clean it out ! Get all the oil, baked in cosmoline, metal filings, whatever else you may find... Get it out of there! clean out the trunnion, clean out the receiver; some guys have found so much baked on grease that the bolt wouldn't fullly close no matter what. Get a cheap .45 cal bronze bore brush. Put in the end section of the cleaning rod (the end without the T-handle). Put it in a cordless drill, soak it in bore cleaner, and use it (slow rev's only!) to ream out the flutes in the chamber.
Once you're done cleaning it like this, stop and clean it again! The biggest problempeople have had with Century CETME's is that they come from the factory looking like they've been stored in waste-oil tanks...
Third, some people have said that they have found their cocking tube bent. This could also cause it to hang up. Some people have also found their cocking tube to be installed crooked... this could also cause problems.
Lastly, DO come and check out the CETME and FR-8 forum... the guys there are really great!