I'm going to ask the simple question first: Do you have the long return spring installed on the powder measure?
Now, assuming the answer to the above is "yes" (because if it's no....your problem is solved...find the spring and install it) the only time I have had a problem with the powder measure not returning is when powder "residue" (for lack of describing it or calling it whatever it really is) builds up between the cast iron powder frame, and the "moving" powder meter. To check\clean this you just take an allen wrench and remove the levers on the side of the rotateing measure, remove the powder meter adjustment, and the unit will come out. Clean the inside of the frame and the powder meter with gun solvent and re-install.
I clean the very often as it will get a powder "gunk" buildup and then when I am loadin away, a shell will whizz past without a powder charge. This is VERY BAD as you could fire a squib load, have the bullet lodge in your barrel, then fire the next round and....ugly with a capital "U". I have helped solved the by the installation of an RCBS lock out die. If any brass tries to sneak thru with an over or under charge of powder, my press locks up and nothing moves. That will get your attention real quick.
A lock out die cost about $45. That's cheap insurance when your shooting a gun that cost $400 to $800.
Dave