Distinct Slapping Noise Coming from Bridgeport Series I 2hp J Head

Hey Guys,

I am looking for some feedback on some noise I am getting from my Bridgeport Series I 2hp J Head.
I have a distinct slapping noise on my Bridgeport head.

I believe it to be the splines or hub splines due to the following:
1- Spindle rotates multiple degrees before pulley moves
2- The amount is the same in high, neutral & low
3- I can’t, with certainty, say it gets better with the quill all the way extended down. I think it is just quieter because it is down inside the casting, insulating the sound.
4- By hand there appears to be no additional resistance in any 1 spot of the bearing
5- Removed the cover under the motor. Belt looks nearly brand new, no damage, no black fuzz from stalled belt
6- Noise is loud when using 4 insert cutter with 2” arbor

Questions:
1- Could the plastic bushings really cause this since I hear and feel the clunk before the pulley/belt moves?
2- Can the female spline be replaces? Would that fix the problem?

I tried to capture the noise in a short video, please see link below.
https://youtu.be/PdbgixF2W8g

Thanks,
Whizbang