I haven't seen this addressed in the thread yet.
WHICH Hornady One shot are you using? Yes there are 2 versions.
I bought a pump spray of the environmentally safe version a while back & got the exact same problem, a case so jammed in the die even Hornady couldn't get it back out. (They did replace the dies free instead). While discussing the problem with a CSR at Hornady he asked me the same question, which one shot? It turns out there was a run of the eco-friendly stuff that was horrible, I had that hand pump with the greenish label. When I told him this he had me return it with the stuck die & replaced it with the 5.5 oz aerosol can of spray one shot (the one with the red label.) That works perfectly well & I'd probably buy it again.
Allan Quartermain: “Automatic rifles. Who in God's name has automatic rifles”?
Elderly Hunter: “That's dashed unsporting. Probably Belgium.”