Hi and welcome to the MD universe!
Looking at your first video, I was struck by the amount of surface material present on the disc's upper surface. Normally they should be glossy and without scratches or deposited material. If there is crud stuck on there, then it could explain why the record head cannot contact the surface consistently, and stops.
Do you have another, possibly cleaner disc to try?
Since the machine is new to you, another possibility is that it's the record head itself which is producing deposits, so would be worth cleaning the underside of the record head with some 70% isopropanol to see if that helps. Even if it isn't the source of the deposits, it may have picked some up during the write attempts.