The title sums it up. Whenever the boiler cycles on and the brew pump is running, there is a 1s break in flow, after which flow resumes normally.

A little background:
This is a Silvia V1 I bought from the original owner. He says he only ever ran DI water through it, but never did any maintenance. When I got it I removed and cleaned (Cafiza and a toothbrush) the shower screen as well as the group (Cafiza/toothbrush/cloth. Next I dropped 3g Cafiza in a blind basket and backflushed until it was more or less clean. After rinsing I pulled my first few shots on it.

This is my first machine so I don't have anything to compare to. Other than the issue I mentioned and a leaky steam wand, nothing seems amiss. I'm just now replacing the old cracked group gasket. I'm replacing the shower screen.

I have noticed a couple times that there are grounds in the cup I'm hoping this is due either to the screen or the group gasket but we'll see.

Back to the original problem - does anyone have an idea as to what could be causing that?

Regarding the dripping steam wand - are o-rings a good place to start?

Thanks, Ben

I've been thinking about this a little, and I wonder if it's not something to do with inrush current of the heating element right when it turns on. It's just a brief shutoff (usually 1-2 seconds) and happens right as the boiler light goes on. I can also disassemble and reassemble the pump, but it doesn't really seem like the symptoms I'm seeing warrant that. Would love not to mess with and/or replace the pump if I don't have to.