Have you found an solutions?
I have owned two of these C4 5600. One left one right. I have used the left one consistently for bottom fluking(summer Flounder) with no issues. But the othe other one that has seen less action is giving me the same issue. It wont free spool after opening bail, you need to roll it back a hair then it will freespool. I have dissasembled trying to find a cause the only thing odd I found was plastic shavings that came from the Pinion Yoke which moves the pinion gear away from the spool.
Update. I'm now positive this is the problem. The worn Pinion Yoke is failing to pull the pinion gear away and is jaming up with clutch washer/bearing container. Found these parts at ereplacementparts online.
Many people say toss it, but they are such great reels. Theres got to be a fix. Gonna order those and will let you know.