Nice job lighting the underside of the group. How much wattage are those small lights?
As for the video, let's take a closer look. Keep in mind that this thread is about diagnosing problems, so I've excerpted several key frames for easier reference. The trouble begins early in the extraction:
A full stream has already formed near the handle and beading has only begun elsewhere. Channeling near the front is typically due to uneven distribution as you unconsciously "work around" the handle. It can also be caused by an aggressive lock-in as the group slices the top of the puck, but based on the speed of the development near the front, I'll bet on uneven distribution.
Later we witness other evidence of problems:
It's difficult to see the thin line in this individual frame, but in the video it's easy to spot at least 2-3 distinct fine-mist sprays. This could be side-channeling due to loss of puck-basket adhesion or again uneven distribution opening up small fissures. The white backdrop also shows signs of spattering. In a proper bottomless extraction, there is no overspray.
Finally, I'll zoom on this last frame to point to another sign of an uneven extraction:
Some color variation is expected and desirable ("tiger striping"), but this blond streak has the look of a localized loss of puck integrity. Though it doesn't show up until later in the video, colors twisting like a barber pole are another sign of channeling / uneven extraction. In some cases the fissures are bad enough that the stream shape itself will twist (not just its colors). It is hard to judge given the lighting of the video, but it looks like serious blonding began around the video's 19 second mark.
As you've read in your other thread, Silvia has a reputation for being finicky:
another_jim wrote:I'm no expert on the Silvia; I just got a pair in order to set up an espresso tasting lab. From what I can see so far, the machines have a huge tendency to center channel and underextract the basket edges, at least when using my usual dosing and tamping techniques which are designed to prevent side channeling (the much more common problem on E61s and the Elektra). The result so far has been distinctly inferior tasting shots, both for flavor and for mouthfeel.
I'm pretty sure one can compensate for this by modifying ones ritual or blocking some holes in the middle of the shower screen; but there's no doubt that going to an E61 or other machine with a well engineered group is a good sized step up in terms of everyday, gyration free consistency.
That said, you can absolutely pull good shots on Silvia, but she's a harsh mistress. I recommend starting with the
WDT to cure the distribution problem and reviewing the
Troubleshooting Checklist of
Perfecting the Naked Extraction.