Clean the barrel and hop rubber, see if the issue has gone away.
if it persists, check how the hop rubber is sitting on the barrel and that it’s central. You should be able to see if the contact patch is in the centre of the barrel’s rebate.
If that was central and everything is clean, it’s likely the hop arm is slightly deformed and putting more pressure on the near side of the bb than the far side. This can be remedied by bending it back into shape to give equal pressure on both sides of the bb.