I'm gonna go out on a limb here and say its not your machine. I wouldn't expect a machine problem to just happen all of a sudden, but who knows.

I really suspect its a grinder thing.... and although Toscano is pretty forgiving, I think you need finer control on your flow.

I'm not in anyway going to claim to be an expert on espresso, but I can give you my recent experience. I've been using a Rocky grinder for 14 years. A couple of months ago I started having a severe channeling problem. Part of this problem was caused by the fact I don't use my espresso machine on a regular basis and sometimes it's a few months between using it. Old fart CRS had me dosing at 15 grams after a three month break instead of the 14 I had always used and was over dosing, causing the screen to disturb the puck and causing side channeling. Well, I started changing everything one could imagine, and when I finally figured out what was going on, I went too far the other way and was under dossing, causing a host of other channeling problems. I started doing all these voodoo techniques and everything else one could think of, so by the time I finally got everything figured out, I had to complete relearn how to make good extraction.

As with your situation, many accused the Rocky grinder as one of the main causes of my problem. I finally bought a giant size commercial grinder and modified it so it was practical single dose, home use. After getting all the problems worked out and making good extractions again, I've gotten the Rocky grinder back out and tried it. I have no problem getting a good extraction with the Rocky. Granted, you don't have the infinite variable control with the Rocky so you can fine tune the grind for the precise extraction you might want but there is a way around most of that with your tamper. One of the easiest ways I found to adjust was to use a straight tamp when the grind is set for the extraction I want, but if it was too course and giving me more extraction that I wanted but the next click was too fine, I would just nutate the tamp and not tamp quite as hard on the higher setting and that slows it down to the dose I want.

One thing about this fangled nutation tamp, I've seen video's and read all kinds of descriptions of how it's done but it was not until I was watching a video of Matt Perger and paid close attention to how what he was doing that I finally got it to really work for me. First, I think it takes a custom tamper made for the size basket you are using because if you watch, the very first thing he does is do a soft tamp and then locks the tamper back toward him in the basket. Then he goes around the basket twice with minimal pressure and keeps the tamper locked against the side of the basket while going around. He then straightens it and does his final tamp. I think if a tamper is not fitted for the basket, it going to be hard to get that angle of rotation right. I know I've tried it with smaller and larger tamps than one that's sized for the basket and it didn't work for me, but with the proper size tamper, it works great. Now, understand, this is just my personal opinion and as I said in my first sentence, I AM NOT, by no stretch of the imagination an expert on any of this espresso stuff.

I've gone back to using the Rocky as much as I use the big grinder because I don't just use one espresso blend, I also use the espresso machine to brew my coffee and I use several different origins coffee so I use the Rocky to grind my coffee and the big grinder to grind the espresso.

One other problem I have realized over the years, when you install new burrs in the Rocky, they require some seasoning just like the big grinders. That was part of my problem I was having, I had recently replaced the burrs in mine and it took several pounds of coffee before things it became consistent again.

Does the Rocky grind as nice as the big grinder, by no means, shape form or fashion. Is their a big difference I the taste between the two, I don't know, I don't drink straight espresso's. All my coffee drinks are with milk and sugar. I can just say the Rocky give me just as good of an extraction as the other grinder.

As for the wasted grounds, I find it only take about four beans to push that small amount of grounds out of the chute. This can be done by adding an extra 1/2 gram of beans and sticking the porafilter under the chute after that little clump falls out or just throw three or four beans in it and push it out. Yes, the Rocky dosserless does give a clumpy looking grind, but I've never seen this to be a problem. I still just give the portafilter one firm tap down on the counter, level it, tamp it and stick it in the machine.

I hope things are progressing along nicely. It's makes the morning routine misserable when the (in my case) one thing I really look forward to is that first cup and it stinks.

I didn't see it mentioned so I thought I would ask. Have you cleaned your portafilter? It can make your coffee turn quickly if not cleaned and/or rinsed regularly.

Thoroughly clean your grinder.

Update. I decided not to replace my Rocky burrs, but rather to upgrade to a Baratza Vario grinder. The big steps on the Rocky always did bug me, so it will be nice to have something that offers finer adjustment. Can't wait for the Vario to get here!

I did try cleaning the Rocky as best I could without removing the burrs from their carriers. (I couldn't get the screws to budge. The slots were very shallow, so even mild torque made them begin stripping. I didn't have the patience to Dremel the heads.) So far, no difference in the cup.

I do think something is weird with the Rocky because I'm keeping it at 7 clicks above "soft zero." Yet, if I lightly place my hand on top of the hopper, the burrs start to touch again!

Ironically enough, while Toscano tastes like an ashtray, I' experimented with and have had pretty good shots from STARBUCKS HOUSE BLEND. It's not my desired flavor profile, but I've had good crema, low bitterness, and overall pleasant shots from it. What gives!?

STARBUCKS HOUSE BLEND. It's not my desired flavor profile, but I've had good crema, low bitterness, and overall pleasant shots from it.

What gives!?

Double negative....

Can you try to vacuum your grinder?

I bet the reason you are ok with Starbucks is that your lucky to get the proper extraction. Plus it Starbucks espresso blend is very roastsy so you're probably tasting more roast than anything else. Toscano is a bit more refined so you may need the finer control over grind to get the proper extraction.

Also don't think your problems are over with the Vario. I used one for 3 months and got rid of it. The plastic burr carrier makes it very difficult for it to hold grind settings.

Hmm. I'm pretty sure the Vario has an aluminum burr carrier. I had read that the Preciso has a plastic carrier, though...

Take a look at page 7 of this thread (SCAA 2013 Reports). It shows the picture of the Vario and Forte burr carrier.

Here is the pic....