When my (new to me) TD-124 started to slow down after 1 side, I thought it was the motor.
I rebuilt the motor, that wasn't it.
I thought maybe the belt, that wasn't it.
I tried different lubricants, that wasn't it.
I fell asleep during an album side and when I awoke, the platter had seized. I suspected the Nylatron main platter bushings so I reached out to an Engineering Materials Forum where I got my answer. The material Nylatron expands as it heats up. It's useful as a drawer slide, not so good for spindle bushings. Friction from the turning spindle expanded the Nylatron bushings until they seized the spindle.
Replaced them with Sintered Bronze and all is well.
The internet is a great tool.