Visible seam in the solid mesh

Hi guys,
I made this simple model but I have a problem in the seam area. In one of those seams, I have discontinuity and visible seam in render mode. How can I revise it?

Explode, untrim, match surfaces, trim, and join back. If you in a hurry, than trim just the portion with a seam, and blend it.


Thank you very much. It worked. I learned something useful from you. Thanks.