On my Rocky, I can start to hear the burrs contact at the "0" point on the label wrapped around the coffee filter.

I grind my espresso 4 or 5 clicks above that "0" point and I get a 25 second extraction from 17g of coffee in the portafilter.

Just FYI.

My experience has been that:

1. Stale coffee will allow water to run through like diarrhea. I almost never grind anything that is more than 2-3 weeks past roast.
2. Due to tolerances, a grind setting that produces audible burr contact when running the grinder without beans will not cause burr contact when the grinder is grinding beans (i.e. the beans push the burrs apart a bit)

My Rocky is remarkably stable so long as I am good about what beans I put in it. That is, I almost never touch the grind setting and when I do, it's to adjust from 5 clicks down to 4, or 4 up to 5. This is after a year of use and probably 50 pounds of coffee have gone through it.

One thing I would do is take the hopper off and remove the burrs and make sure they are clean. It's pretty easy to do.