I have a Breville Express, 870XL I think, (single broiler, built in grinder). Lately during pre-infusion, a lot of coffee has been coming through before the pressure ramps up, while it's still low and in pre-infusion.
If I put the grind size very fine (a 3 or 4 on the dial) I'll get less during pre-infusion, but even less during the real extraction and also it'll be sour or whatever; you can't taste the flavour of the coffee. This happens both with the single filter and double filter.
I've had the machine for 6 months. Surprisingly the descale light has never come on, so I've never descaled it. I'm trying to keep the grounds even and I use the razor to even out the ground at the end (I blow out excess grounds dug up by the razor).
I'm not sure how to troublshoot this, beyond the different grind settings I tried.
EDIT: I am manually tamping. It looks even when i tamp and I usually tamp as hard as i can without putting my body weight into it, then I use the razor. I try to dose enough, such that after i tamp, I can use the razor to clear off a little from the top, so I know it's even.
Is it possible it's just the beans? This all started when I got new beans from a super highly rated cafe in San Fran, I think. They were already 3 weeks old when i bought them and it's been 2 weeks since then. I just didn't think it would matter for water going through pre-infusion... like how is there even enough water to go through the puck during pre-infusion, I assumed it would barely be enough to wet the puck.
EDIT: Using a fresh decaf bean now from Monogram and I'm having the same issue. It perplexes me that water flows through during pre-infusion and I ALSO still get espresso ranged pressure during the main extraction. Like, if water flows through with no pressure, then shouldn't it flow through faster with lots of pressure? Or instead shouldn't it be impossible to get high pressure, if water can flow through with no pressure? The physics of this whole thing confuses me.