It could be a problem with the cable or the motherboard, but I think the most likely explanation is that the drive is dirty after decades of service. If the drive is reading disks the read/write heads are probably fine, but some of the sensors could be blocked/stuck. If you feel confident enough to take the top cover of the drive off it should be easy to see where dust/dirt has built up. Pay particular attention to a series of little black posts. Give them a little scrub with a q-tip/cotton bud and isopropyl alcohol and they should free up. Be careful not to disrupt the read/write heads and thus misalign the drive.
