if it has a bail its not a bait caster, I have seen line on a bait caster (mostly braid) not spool because its spinning on the spool but if the reel has a bail its not a bait caster and if it is going up and down and the bail is spinning there is only one possibility of why its not reeling in. the line is probably going straight to the first eye and not going through the bail lolIf it’s a baitcaster and has a full spool of line, I couldn’t see it slipping. OP, when you reel does the spool spin but not the line bale? Or does the spool not spin/retrieve?