Bosch Dishwasher starts, drains but doesnt spray water just hums?

As per the numerous answers about tipping the machine to the left-lots of water on the floor -hey presto the machine now sprays water and happily churns away. However after going through the majority of the programme it stopped. So I moved the dial it started going again - water coming into to rinse ran for 5 minutes and then went off again.
Moved the dial and it is carrying on as normal.
Why?
What is the purpose of tilting the machine to the left- what is it actually doing? Obviously I cant keep tilting it to one side every time I want to use it.
What is the issue that is stopping the machine?
Is it the impeller that needs cleaning of gunk/debris if so where is this chamber/pipe?
Or is it gunk in the waste?
The salt chamber- what should I do with this?
Model is SMI 5081/11 Classic old model
Thanks