Delta Single Bath Faucet leak

Hi,

My Delta Single Bath Faucet is leaking under the handle.

Here is a link that shows it: Troubleshooting a Leaking Faucet : Delta Faucet

This seems easy as I have repaired it before. But this time it is not working.

I replaced the ball and cam with known working ones but not brand new and it is still leaking. I have tightened the cap and it is still leaking.

This seems odd since the parts I took out (ball, cam, packing or seal) work fine on the second sink.

Any suggestions to repair.

Thanks.

Delta Single Bath Faucet leak