I think you might have got the issue i was reporting wrong.
It was not, that the truck was "sliding" on that slope, but that i was no able to enter, even though it was moving only minimaly (if at all)
i'm not sure, but i think i had been able to enter sliding trucks at previous occasions, but they might have stopped as well
navertheless, watch the video, and then decide:
if you disagree, just nevermind and close this (i'll apologize for bothering you, in that case)