Slip yoke will not slip on...

For the life of me i'm not sure What's going on here?
I've used this slip yoke before end it's in good condition.
I just had the transmission completely down and see nothing wrong with the splines...
I get it halfway on and it just stops?.. And when it stops halfway on it sticks as if it's jammed on some??? I actually have to take a hammer and slap it back off...
This is a very odd one...
I lubricated everything got a flashlight and looked in the tailhouse and seeing nothing that should have struck it and of course looked inside the slip york nothing...???
Any help mary ideas are appreciated...