Still puzzling over the solar hot water

At the start of the year I posted about us not understanding why the solar heat doesn't load the tank correctly. We still haven't managed to understand what is wrong. We have however got some thermometers which we attached to the three pipes and were able to tell a bit more from this.
We have emailed the installer again and also Akvaterm the supplier of the tank and the controller for loading the tank. It is frustrating because it means we are not getting the energy from the sun that we should.
Overall the system is great and the energy we do get from the sun is a useful boost to burning wood. It would be EVEN BETTER if we could get it to work properly though. The installation is a bit frustrating because the guy who installed it lives miles away so cannot just pop out to look at things. We have found 4 issues with it.
1) The pipes to the radiators were plumbed the wrong way round (so it took out from the cold end of the tank and put back in to the hot)
2) There was a leak in the solar circuit (and still is)
3) The heating controller isn't attached as per the Akvaterm instructions and was done incorrectly even for what the installer had intended
4) This issue we are looking at here where the solar energy is not loading correctly to the tank

This is some diagrams where I was trying to understand what the LK820 controller is doing.

This diagram shows how it should all be connected up. The heating on the right hand side isn't done quite like this as on here there is a 4 way valve that mixes from the top and middle puts back in the bottom to keep stratification, ours just takes from the top puts back to the bottom.