vid3 and vid4 look the same to me. i.e. VLE1 makes no difference
vid5 and vid6 look the same to me. Software Scroll is working fine.
vid6 has a "different" white scan line #184 @ 0:04s
I have concluded that your hardware is permanently broken at scan line #184. It remains white when INVERT SCREEN is shown @ 4:03s
I have also concluded that the S6D0139 can display two Partial Screens but is not capable of doing a "BAND SCROLL"
I will post a sketch shortly to show the Partial Screens (and hopefully a VERTICAL SCROLL)
Many ILI9320 style controllers can do Partial Screens. Some can do one, others can do two. So at least I can try the sketch before I post it.
David.