John_R81...
Your initial post didn't have most of that information, and I got the impression that the wing just rode up a few inches then dropped down again - not that the pilot was fighting to keep the aircraft on the taxiway.
I don't find your pictures terribly helpful, because I don't know how tall the van was other than that it was 'a few inches' higher than the tips of the wing.
'A few inches', as you originally stated, applied to a wing half-span of 5 metres wouldn't have produced more than a degree or two of bank which the pilot may not have noticed, or could have ascribed to unevenness in the taxiway. From the fact that the aircraft lurched to the right after the (presumably) left wing dropped implies to me that the pilot was probably using a lot of right brake, and therefore must have noticed that something was wrong. I assume the conditions weren't gusty on the day?