We have a twin bottle setup with a valve that has a turning lever in the centre with an indicator that goes red when one bottle is empty.

It appears not to function well.

If one bottle is empty and one is full, flipping it to full one does not restore the gas supply. The second bottle must be replaced before it works. This seems contra to logic.

Is that how it is meant to work or is it faulty?

Also, is there an option where the changeover happens automatically rather than manually?