Help with Condor valve disassembly

I just bought a new Condor valve to install on my tank but I was going to take it apart for polishing and o-ringing before installing. I pulled the grub screws out of the tophat but it will not unscrew all the way off. I tightened it all the way down and I can see the last few threads of the valve stem and they look ok but for some reason the t-hat will catch on the last couple turns when unscrewing. It catches enough to where the drag overcomes the return spring and the whole valve stem spins with it.

You guys have any tricks for getting these apart without damaging them?

Thanks