Cam bearing issue

Cockeyed bearings, distorted cam tunnel bores, bearing or cam journal on the high low side tolerance or micro debris...dry start.... all potential causes.
Scrapings good, even scotch bright dish pad wiped over a time or two where its tight/leaving dark marks of contact.
Cases of older engines where they fall apart can be do to the corrosive agents/contaminants in infrequently changed oil. Blow by makes the oil darken quick with an older engine, so more frequent oil changes become mandatory or this will hurt the factory's lead bearings. Other times where someone decided to put a cam in and some heavier springs...on say..some 40yr old contaminated bearings.. they can too fall apart.