The only thing I didn't see mentioned here was, when you changed over to lithium batteries did you also change the controller. I might be corrected about this but, I have heard that the normal MPPT controller doesn't like lithium because there is a subroutine in there that does a sulphide correction on your lead acid batteries and lithium doesn't like this and can damage the batteries. Apparently you can get MPPT controllers that allow you in the settings to turn this function off and then are acceptable to lithium. Just to explain where my " expertise" on this comes from, I have lived in my mobile home for 14 years now the solar consists of 4x 300Ah deep cycle batteries, 8x 300watt mono panels, controller and inverter are VIctron I also have a 6.2kva diesel genny. As a by the way I did change the batteries after approx ten years as one wasn't performing and not worth mixing old with new. I have no 12 volt in the van and all the components are household items, the frig,microwave, hot water system are all household items. I do have a 2000watt hot plate, four burner gas cooktop and have built a removable solar collector for the hot water system. The only " caravan" specific item is the aircon unit which I reluctantly put n when my split system unit finally spat the dummy. I only mention all this to show that if you set your solar up properly with good quality items you can expect trouble free power for a long time. And the secret to a good system is to get good info from a good supplier and set the van or camper up completely seperate and stand alone from the tow vehicle
Regards Kev