UPDATE: See bottom of this initial post for the solution I found.
Uneven extraction on bottomless portafilters and a subsequent unlevel puck after the shot.
I haven't used a ridged basket in a while so when I used one over the last week I began to notice that the puck started level after being tamped and after the shot it was unlevel. The unlevel part is where the puck first starts to bead. No matter how much WDT, lately all my shots seems to start beading on the right before the left. Sometimes they end up coming into a single stream but there is definitely a pattern.
I have tested everything I know to test. I use an IMS screen but have also tried (with similar results) on the stock shower screen. I have put a level on my counter top, various parts of the machine, group, basket, portafilter, etc. Everything is level.
WDT with Kafatek tools helps but does not eliminate. I use a LevTamp and have tried lighter tamping and harder tamping. I use VST baskets so I have tried going back to stock; stock baskets aren't quite as sensitive but still exhibit the same behavior. I have used all E61 preinfusion tricks to lengthen the time for the puck to saturate (trickle PI, pump on then off for several seconds, etc). It just seems like the water flow is just favoring the right side.
After reading the plethora of information on here on possible fixes with nothing really helping, I started reading more about the E61 water dispersion. Apparently, that screw in the group doesn't do a great job of even water flow, which the screen is supposed to fix. I feel like my water is just more pronounced to the right side for whatever reason and the screen isn't offsetting this enough. Are there any 'tune ups' that can be done to that screw?
I've been going through a lot of coffee. I had originally thought my issue was head space; however, I did the Schulman 'dial in' method Friday using the stock basket down to 14g and again, while not bad, it still favored the right side and had a gentle slope to the right when done.
You hear a lot on here about how 'forgiving' an E61 group is but man this has been frustrating. Any other ideas?
NOTE: I'm using a Sette right now but I had similar experiences using a Monolith Flat so I do not believe the grinder has anything to do with it.
UPDATE 7/7/17. My Solution:
After changing to a thicker gasket and inspecting my prior gasket, and pulling about a pound of coffee, I am ready to say that I have found the solution. I am so relieved to know it has nothing to do with my machine / grinder / technique. It also wasn't entirely about the size gasket I was using. I think 8.5mm is recommended but the 8mm is not what caused my issues.
My gasket was either warped or a lemon from the OEM. I got the idea to measure the size of my gaskets from a user posting about measuring his to be 8.2mm. I have always assumed the stock Profitec ones were 8.5mm based upon what WLL told me in a chat. I started by measuring my stock gasket which was around 8mm. I believe that it was originally 8.5mm but after 6+ months of use it had compressed to 8mm (same with the user whose is now at 8.2mm -- i'd say it started at 8.5mm). From what I understand on stock style gaskets, this is normal due to them being rubber and being compressed / heated / cooled etc. It also makes sense because the PF had locked in closer to 5PM instead of 6PM prior to me switching out for Cafelat.
So let's talk about the Cafelet gaskets. I bought both the 8mm and 8.5mm gaskets. I found the 8.5mm a bit tight so I had been using the 8mm. I had a little issue installing when it was brand new but eventually got it installed. For nearly 6 months I've had some issues that seemed to be getting worse. I assumed it was coffee, or the grinder, and then my machine which started this thread. It had nothing to do with any of those. I measured the thickness of the gasket this morning. Low and behold it is 8mm in places and in one quadrant it is 7-7.5mm. Whether this is compressed/damaged from my first installation or a lemon gasket, I'm not sure. But now it all makes perfect sense: uneven pucks, extreme channeling, etc were caused by the gasket sealing unevenly.
I had never thought about measuring the uniformity of my gasket. What a simple fix. Back to picture perfect pours!