Hmm, actually I've never tried to unscrew mine. I assumed they could be unscrewed because I thought I saw it somewhere.And I've just tried unscrewing mine, you're right. It's difficult without some leverage. Maybe you can put something through the hole, and grab the piston face to unscrew as hard as you could?

My piston on the other hand looks pretty straight to me. Don't think that's the cause in my case..

According to OE, the piston rod and head are screwed together with high strength loctite, so you need to heat it up to remove. I tried using a butane torch but still couldn't get a good grip handholding (with welding gloves) to undo them. I ended up getting a new set of piston and rod from OE and with the OE seals, I no longer get any stream of water coming through at halfway, so I think my supposition that the misaligned piston head was causing the issues was correct...

Bostonbuzz - Did your fine mesh dispersion screen mod help your puck divot?

Scythide - Did the crooked piston shaft make a difference in your divot problem once fixed.

I get the same dent almost every time. Especially when using lighter tamping methods.

Possepat: I ordered a fine stainless steel screen, unfortunately, I can't find my order so I don't know the fineness of the mesh. I settled on 3 stacked discs that I cut (make sure they are smalled that the cylinder or you're dispersion screen will be lower). My channeling, "dent" problem is solved.

Overview of what I've gone through to fix the irregular water dispersion/shooting water geyser:
1. rotated piston 180 degrees (didn't do much)
2. Got the official seals (did a little)
3. RAISED my pressure, because it turned out to be super low. (Didn't do anything)
4. 3 stainless mesh discs above dispersion screen (90% better)

Things (all done after the above list) that made the coffee go from still bad to amazing:
5. Switched from my usual lightly roasted beans (Problem Completely SOLVED)
6. Used Elektra Basket (Espresso to die for)
•Note, the elektra basket wasn't working for me, and then the "stars aligned" the other day when I switched coffees.

Whether I have fixed those issues or not, 4, 5, and 6 were the big improvements (hence the bold). Currently, wether erroneously or not, I think some creminas just have a weird phenomenon going on. In a couple weeks I may take the screens out and see if my results change at all, debunking my theory It may have just been the coffee and basket!

I did not have (at least to my knowledge) a divot issue, but I did have trouble with water coming through the seal (more trouble with the OE seals than the official ones, but still some issues with the official one) before it should have. I ended up replacing the piston and rod and since then have not had any of the same issues with either of the seals. However, the official seals perform a bit better in my opinion (smoother action).

Thanks for the quick replies guys.

Bostonbuzz, I already ordered a couple of 1ft sq sheets of stainless steel mesh from ebay. One is 80wire per inch the other is 100. SUPER cheap all things considered... I had a hunch this was the way to go, even before I first seen it mentioned on this thread. IMO I think it has to do with the orientation of the water inlet port in the cylinder and the fluid dynamics of how the water comes through there and hits the puck. Tamp, bean and grind also seem to have a significant bearing. I've got a nice hole punch at work and I'm hoping I'll have a size that will be perfect for the cylinder. Did you have to adjust your piston rod stop and lock nut to allow for clearance between the piston and mesh?

I wasn't willing to adjust it, although the nuts are already turned down as far as they go. The piston his the screens with about 3mm to go, but it has since flattened them down a bit. Part of the problem is not really having the tools to cut the screen cleanly. I'm sure yours will fit much better. If your screens don't do the job, I would Rex omens finer ones. Just for a reference, put under the faucet 6", my screen collects water on top of it, but I'd go with a finer one if I did it again.

Puck Dent Update,

After performing Doug's recommended maintenance (111,Piston cylinder clean, pin lube) my puck dent problem virtually disappeared! The lever lifted soooo much more smoothly and the piston no longer made jerky movements on the way up. Also banished was that almost sheering rubber sound the seals made on the cylinder wall.

Problems which I contend would uncover the inlet port in the piston too rapidly and with little control. I will however still install my superfine stainless mesh screen as I feel it will aid in more even dispersion and keep larger solids from finding their way up into the cylinder.

I'll keep you updated, and I'll try to remember to take some pics as well.

That sounds really promising! I remember the last time I checked and cleaned, they looked pretty good. Maybe it's time to clean the grouphead+cylinder again and to reinstall the new seals. Thanks for the update!

Wow am I glad things seem to be looking up here. Just to add my experience with a divot. I have been noticing a large divot that is always in the same location. If I tamp aggressively it does not show up but with a light tamp it is prevalent. However, it isn't always there. I can feel the difference in resistance when the channeling occurs and when it doesn't. I am not sure why this would be. I bought my Cremina 5 months ago and at the time OEM gaskets were all installed. This is only one data point but assuming this to be the case my Olympia seals are allowing a divot to form as well. I guess I am suggesting that there may be a problem outside of the manufacturer of gaskets. I really was happy to see that some lube and cleaning may do the trick and so I will certainly be doing that in short order. I will also look to see that my piston shaft is straight and will provide that information as well. It is curious so many of us are having this problem eh.

Thanks for keeping things up everybody and I will let you know what I find out.