Mine did this and after cycling many, many dummies through it and watching everything that was going on, I found that I had to clean up the grooves in the guide rails on each side of the receiver. The grooves are what the rim rides in as the cartridge moves slightliy forward and then up/forward (diagonally) toward the chamber as the bolt pushes it forward.
Prior to that, the drag of the rim on the very rough lifter (carrier?) was causing the cartridge to try to enter the chamber with the nose too low. I polished the trough or top side of the lifter and that problem went away but then the rough grooves in the guide rails took precedence with their own probelms.
Where the grooves' horizontal portions meet the diagonal portions, there was a ridge of metal and a point left over from the machining which had to be "softened" a little. As the rim hit that intersection, the nose of the cartridge would tip up because the rim was still too low at that point along its horizointal travel. Putting a bit of a radius at the intersection (and polishing it) allowed the rim to start moving UP sooner as it was moving FORWARD and solved that problem. There's not a lot of metal tp remove, so it's a fit/try, disassembly/reasse,bly process which can take some time. The rails can be removed without complete disassembly though. Makek sure you keep them even (symmetrical) to one another. Mine werent from the start and still are a little off but not enough to casue problems - just try not to make it worse as you work.
At the top of the feed rails, these grooves are visible opposite one another, where the rim pops free of the guides. Pushing the rear edge of the grooves at this point BACK, toward the rear of the receiver allowed a longer COAL. I did not gain a lot in COAL, but I did at least get it to where it would feed correct COALs. It still willl not feed anything unusually long but the nose shape of the bullet has a lot to do with that anyway so playing around with bullet shapes and COAL can help too. This is where a LEE factory crimp (the RDO version will not re-re-size your bullets) comes in handy. If you seat deeper, pay attention to powder charges. You may have to bacjk off a smidge.