Greetings,
Start by gently running your finger tips up, down, and everywhere trying to sense a raised burr.
With the press mounted to a solid bench, apply black felt pen to the shaft and let it dry.
Next, gently attempt to place the tool head only on the shaft.
If it sticks, stop and remove it.
Now look for wear marks on the felt pen application.
All of the above is with the assumption that all the parts are Star. No Phelps pieces.
Go slow and observe any abnormalities.
With good fortune, it may just be a burr.
Cheers,
Dave