Never believe dealers.. of anything.... contact factory... for real answers...
double up on straps... 4 are better than 2.. every time. my opinion.
and always check straps.. at 25 miles and 100 there after... they are not made of STEEL.. so can stretch/slip... and install errors...
I deal mostly with motorcycles.. 40 plus years.... I use 6 straps for 1 bike.
that is (6) 1000 pound straps.. for (1) 700 pound motorcycle...
but I have used tow dolly.. several times...just last year.. Wife's PT Cruiser.
as for the problem... you go to them and fix it...or direct them to a trailer rental place to correct issues.