Sure, thank you very much. I just uploaded my model.

I just realised your reply, thank you.

Adjusting the height did help a bit but if there are a lot of MUs in a line, they are still jumping on each other.

That's the same what I did.

I couldn't make it work with WP lifters and stoppers and using the "Guided Transport (Script)". 

I made a work-around with "Transport Surfaces (Script)" and a little own script for alligning the WPs when lifted.

Anyway thank you for your help.

Thank you for you reply, Viktor.

Your video shows exactly what I am trying to achieve.

It works with only one MU on the conveyor but with several MUs in a row they're starting to jump around on each other when blocked by the stopper. 

The stopper is on layer rvTransport and the MUs on layer rvMU.

Did you change "Box Collider" or "Rigidbody" properties in your example?