Have you found the actual source of the leak yet? You say top but do you know the specific location?
If you have some star san spray it on all the connections. On the posts at the base and on top (the poppets), around the rim of the lid, and on the pressure relief valve (if it has one). Charge it to 30 psi. You will see it bubbling where it leaks. Then you can diagnose the problem better. There are many things that could be causing the problem, so you need to narow it down.
Could be a bad poppet, post not tightened down enough, bad or not lubricated o-ring, loose or worn out pressure release valve, or a dent in the lid itself.