Took my Dillon apart and got a little surprise.

[Rinspeed]

My SDB was feeling real stiff the last couple of times I used it so I decided it was time to yank it apart for a good cleaning. Well I determined the stiffness was coming from the pivot point at the bottom of the handle. After removing the set screw I tapped on the pin with a hammer and dowel. It didn't want to move and I wasn't sure if it was pressed in or not.

It finally came out with several good hits and it was quite apparent was the press wasn't cycling smoothly. There was a good amount of galling on the pin and frame holes. I polished the holes with a drill bit wrapped with scotch brite and the pin with my die grinder and a buffing pad. After giving the pin a good coating of slide glide I put it back together and it works 100% better. I know Dillon says the SDB doesn't require any lubricant but this is one part that requires some attention.

 

[OKFC05]

I've noticed the primer dust from the decapper acts like ultrafine volcanic ash and gets into everything below the plate and has to be cleaned out. The almost invisible accumulation causes galling and binding.

 

[jubela#4]

Depending on the age of your Dillon SDB it may be a candidate for an upgrade from the factory. The older machines had some of the bearings made out of a plastic material, they now have upgraded these to brass.
My SDB is an old one but I have never had the problem you describe and I have loaded many thousands of rounds. They are great machines and Dillon has great factory service.