I use both .....I have had not had any major issues?Are you taking rifle or pistol dies? Pastera was taking pistol dies.
A Lee Pistol FCD uses a collet style crimp die teamed up with a carbine sizing ring just like a sizing die.
The result is usually an undersized cartridge that in turn squished down the bullet inside the case. It’s pretty well documented over on castboolits.
A Lee Rifle FCD is different. It uses a collet style crimping die with no carbide sizing ring.
If you set up your sizing die properly and you load the right size bullet the chances of needing a Lee Pistol FCD are pretty slim. I load some well oversized bullets in different cartridges and have never run into a round that was too fat to chamber.
Take out the taper crimp/roll crimp part out and run just the carbide through, see if it "over crimps" ? In the posted picks it looks like a roll crimp mark?
Another thing to do is take your loaded round and insert into the FCD and see how far the case actually goes into the die ? You might find that the "carbide ring" is really not the problem.
now if your cast bullets are over sized--- more than .002" over you might have some issues.
I do think for the most part that the lee pistol FCD are not generally designed for "cast" bullets. figure lee takes a "average " of case wall thickness and a "451" bullet diameter to figure out its carbide ring size.
Now toss in a cast bullet at .452" plus coating plus case wall variation...ugh, you might end up with a squished bullet