Channeling [BDB/Mazzer Philos]

I WDT and use a self leveling tamper. I've tried with and without distribution. I’ve used an X64 and Mazzer Philos grinder. This happens even when total pull time is 25-35 seconds for an 18 gram shot. I’m getting channeling most of the time. It squirts out the side, and the puck doesn’t pull away from the basket cleanly. Is it possible there’s a problem in the group head causing uneven water flow?