Weld seams showing through new paint job

[xtrmeta]

I believe it's a cemical reaction by some of the paint products.
It happened on my T/A and my truck.
On my T/A all the body work was done about two years before it was painted. The car sat with the final primer already block sanded out to 600. Gave it a once over and painted and buffed it. It looked great. Then about two weeks later the welds appeared.
I used PPG's Global line.
I welded a hood scoop on my truck also using PPG and the same thing happened.
The T/A was epoxied primered first then high build.
The truck I just used a combination high build sealer.
So I belive it has nothing to do with the prep work. I spent three years doing body work on the T/A to make it perfect.
I think it's the paint when it dries shrinking everything under it.