Thought I would post the solution to this mystery. After removing the right fender ... it became obvious that there had been some repair done at the seam pictured in the red circle below .. probably some accident that had not been known to the previous owner ( the third owner ) and not reported on Carfax.
Applied over the seam that was apparently welded was some substance .. something akin perhaps to JB Weld. Some of it still remaining in the second picture. After scraping off the substance, the tapping/stress release sound in the video at the beginning of this post vanished. The car is put back together with no more noise. Thanks to all who gave advice.
