Maybe not enough tension while spooling the copper? I have 300 of 45 lb copper on a CV55 and have a spool of 300 yds 50 lb PP with roughly 500' of 20 lb mono behind that to keep the spool full. I have a 200 Copper on a CV45 with plenty of PP backing, but I will add that I like my reels FULL FULL FULL (almost touching the levelwind) with all the gear on it.
I've been told that our reels function smoother when they're full, or as full of backing as possible. Who knows but it's fun messing with it!