@Snark
Thank You for the quick reply. I sure would have done the above suggested steps if it the same set of ships have never docked with each other, EVER. But prior to this, it had docked perfectly, and then due to a stupid mistake of mine that's totally unrelated to docking (wrong cargo bay size, mission to capture a rogue floating part in career mode), the ship was severely damaged. So now I reloaded to the prior launch stage, put in the correct size and relaunched it again. But only now it doesn't dock. Plus the port is opposite to the corrected part, so no dependency of the port on the new part.
I would do the bug hunting method you suggested, but lack of free time and the reason stated above are preventing me from doing this.
As for the exact problem,
This sums it up perfectly. Only "state=PreAttached or state=Ready" doesn't work because its already in Ready position. Plus I'm trying to connect Clamp-O-Tron and CDP Shielded port, which has the same size and shouldn't bother me much.
@KroShan
Thanks for the suggest. I've around 30 dockings under my belt. Would it qualify me as an expert docker enough, master ?? Anyway, yes I have played the tutorial many many times. I'm very comfortable with docking, the process itself is not the problem. It might be the idiotic port acting up. I limit my speed to 0.08-0.1 m/s, and that too is no problem. But whats this angle alignment you are talking about?