Thanks Eldon, appreciate yours and Bob's advice. Turns out that the spring pin was sheared off long time ago and the main pin had moved so that I could not see the spring pin hole and the main pin was rusted hard in there. Here's a picture of the final mess after I had to apply heat. Brake cleaner also worked wonders to flush the pin out while moving it back and forth in the hole. (brake cleaner and heat not at the same time of course).