You have a very good measure.
Read the instructions (with Lee, if they make a suggestion, consider it a command--they don't waste time on instructions and you need to read what they supply very carefully) and consider what you are doing.
Unless you take the measure apart and clean it out, tightening the tension only tightens the two cone-shaped sections into all the powder kernels. This is NOT the way to get the two components to burnish themselves together.
I know this is hard to put up with, but the conical section MUST burnish themselves together and the leakage is NOT affecting anything.
1) Clean out press
2) Reassemble and put a piece of paper under the measure to catch any leakage
3) Throw at least one hopper full of graphitized powder through the measure to attempt to coat the parts with graphite--some powdered graphite can also be used.
4) Disassemble measure and remove any kernels of powder. Return any leakage to the powder can or toss out.
5) Reassemble and tighten tension before adding any powder
6) Fill with H322 and start to throw your charges
7) IGNORE any powder leakage. It isn't hurting anything and the paper is catching it so you aren't losing it.
8) When done, disassemble and clean out any kernels.
9) If you can control you irritation, after a while the conical sections will burnish together and you will only have leakage with very very fine powders--just like many other measures
10) Enjoy the fact that powder throws are so consistent from such an inexpensive measure and stop worrying about aesthetics.
Never force anything when reloading, and that includes adjusting tension on this powder measure when powder kernels are trapped between the tensioning parts.