Got to looking a little closer at how the center latch works. Looks like the upper door catch bar needs to be centered within the "C" slot on the lower door latch. My C catch doesn't go back far enough. That's why she won't let go when I push the button in part way to release the upper door.
The 63 Shop Manual has various adjustments called out on BODY pages 1-25 thru 1-29.
Will report when I try to adjust the center latch.
Roy