I have eleven of them and they all work great single or double.
Take the return spring off and work it to see where it's binding. Make a spring remover out of stiff coathanger wire by bending a small hook in one end to grab the spring and a big loop in the other to grab with your hand.
Ps you probably have the screws too tight.
Bingo, we have a winner. Or 2.
There was some crud in it as
@Kevin Stenberg said that was part of it.
But the main problem was I had the screws too tight.
I had I cranked down to keep the H110 from getting out. Yes
@fiver H110
So basically I need to keep the screws a little less snug and just live with the fact that I am going to leak about .1 or less, a drop, when running H110.
If it is the newer one it has no spring. It works off a ball chain. I had 2 of the new ones and I ordered the lever and springs for them. The lady at Lee said she sells lots of these as no one likes the chain set up. This is all I use for my pistol needs. But not as bad as their auto-drum. It leaks even with h335 and TAC. But it meters imr4895 like butter.
I have the older one, I bought the new "improved" one and sent it back after one use. Like you, I just did not care for the chain set up. Then went back to the older one and ordered a new hopper, which was all I needed any way.
I only use it for pistol loads myself with the exception of H 335 in . .223.
For now I use dippers, a home made trickled and scale for everything else.