I do not think it's related to channeling. Instead, it's a gotcha in the way the double dispersion block design used in the Elektra, Bezzera and Brasilia groups. There is very little space in the water channels, so the suction when the three way exhausts the pressure is fierce. This can suck up the puck like a vacuum cleaner.
Blipping the pump before removing the PF to knock the puck back into the basket is a good habit.
It helps to remove the shower screen and lower dispersion block once every week or two and clean them. If three or four of the ten little holes get blocked, the problem gets worse. You'll need a stiff wire, like those used to clean the steam nozzles to clear any gunk.
It also helps to change the cleaning schedule, more frequent chemical backflushes using less detergent and fewer pump cycles -- compared to an E61 group, there is a lot less space, so it requires less detergent, but that space clogs faster, requiring more frequent cleaning.
I heard some people reamed and widened the ten holes in the lower dispersion block a little. However, there was no report whether this worked or not.