fines in the espresso!

Fines in the espresso!

As I'm getting to know my Nuova Simonelli Musica machine better, one minor thing that I'm noticing from the espresso that this machine put out is that there are fines at the bottom of the cup when I would be finished with the espresso; by the way, the espresso still taste very good. This does not bother me too much as the fines particles is at the very bottom and I can avoid drinking it by just being careful; I guess is the same way as I do like french pressed coffee do not mind the fines.However I can't help but thinking there might be something wrong with my machine? For the reference, I used several espresso machines and the most recent one being the La Pavoni Profesional lever machine which was sold to another coffee enthusiast. With the Pavoni, I did not have this issue.

There are several things that I can come up with that might explain this apparent phenomenom. Perhaps there is something wrong with the grinder? This is an unlikely cause as I'm using a very capable Mazzer SuperJolly which still have a very sharp set of burrs in it; but I do have a brand new set up burrs that I can swap and see what happen. Also, I have a Baratza Vario which I purchased new that I sometime use along with the Musica but also yield the same issue with fines. 

Another possibility is the basket which might have been worn out. I'm planning to purchase a new double basket and find out if this is the case. Visually, I can not find anything wrong with the current basket, the holes are uniform and seem to be the same size as the holes in other baskets that I have come across. Possibly there might be something wrong with the pressure while pulling the shot? The Musica does not have a brewing pressure guage but only one that indicate boiler pressure so I think I need to build a portafilter pressure guage to find out.

Therefore I'm wondering if other espresso drinkers are having this same problem? and what step should  I take to correct this problem?