Gotten to the bottom of it.
Have it down to an art.
You'd think that after all the prep work, the many days of scraping, sanding, de-glossing and priming, a paint job could hardly fail.
And yet ...
A bubble ... a stinking bubble with two thin coats of nice even latex paint peeling off like a bad sun-burn.
That loud bang you heard was my head connecting with the desk ... I've been hiding my failure inside the walls these past ...uh, weeks, frustrated beyond belief and grumpy. Yesterday I decided to just get over it and get'er done (but didn't get much further than some sanding, de-glossing and priming the stupid spot of fail).
Addendum: I did rake my finger nails over the entire expanse of the pocket doors and fortunately, this was indeed the only spot the primer and prep failed. Phew ...