I've printed out some replacement X-Axis Motor and Idler end pieces but the smooth rods slide into them quite easily not to the extent that they wobble but they pull out an push in with very little force ... while they are quite tight in the the parts I'm replacing and to insert or remove them while I can just pull or push using a twisting motion makes it much easier - if this makes sense ?

So the question is ... is this OK or should I at least redo the idler end ?

Personally i think it should be a tight fit for an I3. Also imho i think those 2 parts should have a design change so that the recess has a fixed depth at both ends to prevent any movement

Ooooh ... good idea ... a plug that you can insert and glue into place would be a good idea - thanks.

If the x smooth rods can only be moved by pushing and pulling them along the x direction but not in the y and z, then they should be fine. Movement of the rods along the x axis doesn't change anything since it's the belt that controls the position in that direction. The x smooth rods on my Prusa2 can also move in that direction and it doesn't affect the print quality as far as I can see even with printing at 0.1 mm layer thickness.