Hyundai Sonata Problems

There have been issues with the door locks. I would take it to a dealer and have them check it for you, they can reprogram them if they find a problem.

Restarting the car has the effect of rebooting the computer, that's why the lights go out. You need to have it checked to find the cause; it's possibly a poor connection in the wiring loom, or perhaps a faulty wheel sensor.
 

It would seem to be in the fuel system, so I would be looking at the injectors to find the cause.

Valves bend because they come into contact with pistons. It could be that the belt wasn't installed correctly and the cam timing is out, it could be that the belt tensioner has failed and the belt has jumped a couple of teeth as a result, it could be a problem with the lash adjuster.

It does sound like a problem with a solenoid. Most dealers would send cars with auto transmission problems out to a transmission specialist rather than fix them in-house, so find out from the dealer where they send their problem cars and consult that specialist. You could also consult an auto transmission specialist to get an independent opinion.

The Sonata has a respectable maximum towing capacity of 1700 kg (braked), but only 750 kg without trailer brakes. On that basis you would need trailer brakes to tow your campervan, a good safety measure in any case.

It’s generally done in these situations because it has to be removed to replace the water pump anyway, which makes it a convenient and cost-effective time to do it. The fact that it was done 35,000 km ago might make you question the need to do it again so soon, so have the mechanic check it and if it appears in good condition perhaps replace it, but I would err on the side of caution and replace it anyway.

THEY will be cheaper, but won't last as long. Platinum-tipped spark plugs are used for their longer life and are fitted mainly because America has laws about service intervals and the platinum-tipped plugs help meet the laws.