Safety: Allow the group to cool before disassembly.

Clean shower screen and plate: Remove the shower screen and dispersion plate. Soak in backflush detergent and scrub until clean.
Inspect for warping: Replace a bent or warped shower screen that does not sit flat.
Descale group: Use descaler to clean internal group passages and jets. Rinse thoroughly.
Replace gasket if needed: An uneven or hardened gasket can tilt the portafilter. Replace the group gasket to ensure even sealing.

Portafilter sprays or channels badly; uneven extraction even with good grinder and technique.

Possible Causes