Public holiday
Planning to stock in at arrival (cheaper destination country, less weight) on a public holiday, ..., or a major event in the region. Everything fully booked.
You can camp wild, but do you have food.
I always pack 1 or 2 meals & buy bread as early in the day possible. Cereals for breakfast, in case of.
Road assistance
Do you carry a spare tire ? Most CamperVan's don't. And a flat tire is only one of the issues you could encounter.
With a good road assistance across all countries you are about to visit, you avoid a lot of headaches.
Insurance
Check if your insurance covers the countries you will/might visit. For some countries you might need to ask an extension.
Both your car insurance and your personal liability ensurance.
Administrative issues, sickness, political instability, ...
Plenty of other websites that help you decide what to do.
Small toolbox
Ducktape, some rope, spanners, ... don't weigh much and help you to get to a (repair)shop.