Might be worth trying the procedure of re-seating the metal shielding cover described in I found out what caused my FP2 screen freezes / screen becoming unresponsive ?
That helped me a lot with my intermittent screen problem, which included brief versions of glitches like your video shows, as well as other glitches and the screen just remaining black and/or the touchscreen being unresponsive.
That said, your problem sounds less intermittent; if bending/flexing or disassembling the phone doesn’t change your symptom, then maybe this is not your problem.