Hi,
You may remember I had this problem too! It looked to me like the recess in the seal is to small a diameter for the capsules so it tries to seal on the outer edges only. I was going to send it to Brocock but have instead left an empty capsule in all the time so it is permanently distorted. Try leaving an empty capsule in for a day or so and then try a full one to see if it seals. Not the ideal way to sort it, but it seems to work...