Are mobile supply units necassary

or will regular supply units Supply any unit.
something is wrong with the supply system.
I am seeing supply messages all over the place.
Also no log to know where they go.

There is nothing wrong with the supply system that should be bothering you.

1. make sure you're buying enough supplies
2. make sure you have enough supply units
3. if it still isn't working, disband your units and reform them