I have a really weird issue with my Strega (regular version) : when I pull my lever I do not hear the pump engaging, yet when I disengage water does flow (but not enough, espresso comes out underextracted). What's going on? Is my pump broken or the pump switch (I hear it clicking) and pressure still fills my group a little bit

Pull down the lever without a PF engaged, and see what the flowrate is. If the pump is dead, or the switch is wonky (the more likely culprit), all you'll see is a trickle as the HX empties, then nothing. If the pump is running, you'll get continuous flow. ... careful letting the lever back up ...

If the pump is actually running, the sound deadening foam has slipped into a record setting position - congrats.

I tried a few more times, the pump engages again. So I guess my switch is dying?

Remove the plastic cowling from the top of the lever and take a look. A few times on mine, the switch moved slightly, and the metal bent slightly, so the lever dind't reliably switch it on. In that case, just bending the switch arm a little will fix it (the arm is just a strip of stiff tin, easy to adjust).

Thanks, oddly enough thing started working again but if /when it stops working again I'll first try that before hunting for a new switch