Had to modify dimensions to better fit ballbearing and profile.

Made the ballbearing 'in object'.

Added some fillets and extra material.

Actually the fit is very tight and it sits on the shoulder of the two vertical guides, hence it doesn't need to be fixed.

Z-wobble actually improved a lot!

Instructions

As for me the layer were the ballbearing had to lay allways collapsed I went for an 'in object' solution.

Actually you have to add printing pause at the last 'ballbearing' layer, insert the ballbearing and resume.

First print an object just to check the dimensions being printed correctly as if the ballbearing is not fitting in completely and its surface is not level to the latest layer you risk damaging the tip of your extruder when it will try to print over the bearing.

Just degrease the surface were it will be printed over and don't worry too much if the first layer will not stick.