Yes. The slow rolling offset is caused by the beat frequency between your nom. 60Hz mains supply, which wanders by approx +/-0.05 Hz due to demand on your regional electricity supply grid and the SX64's crystal generated frame sync, again nom. 60Hz. Something is taking the monitor's horizontal scan circuit out of spec for part of each mains cycle, and a dried out main reservoir capacitor in the power supply (causing excessive 2x line frequency ripple on its outputs) is a prime suspect.
Its a pity you didn't shoot the video with the whole screen in shot, and preferably with a grid pattern displayed. If we saw two bands of distortion moving up or down, with each coming onto the screen before the other leaves the opposite edge, it would indicate 120Hz ripple, which is diagnostic of a non PFC PSU with a bad reservoir cap. OTOH if it had a single band, that would indicate either 60Hz ripple possibly due to a bad diode in the mains rectification section of the PSU, or due to a ground loop causing a threshold shift in the line sync circuit. I think we can rule out a bad degaussing circuit due to the good color purity and the sharp transitions between straight scan edges and where its distorted.