I've been considering faulty manufacturing as I've also read about it here but didn't want to jump the gun. Especially since only Kodi was pushing out segmentation faults, underlying OS stayed up most of the time.Pi 3 b+ is also quite a new device so some early adopter issues are also to be expected.
Unless anyone proposes some other ideas or tests to try, I guess I'll be RMAing it and hoping that they wont send it back saying "everything is fine".
Sidenote: I've never had a reason to adjust overscan, I think it should be the default from the install. The picture seemed 1:1 to me.However good to know - as I've never had any issues, I didn't really look at that setting or acknowledged its existence.