It ain't supposed to slip, period! Anybody who says its "normal" don't know chit from Shinola. Could be a worn crank drive pulley letting the belt bottom out on the pulley. Or not enough tension on the drive belt, but all the tension in the world won't overcome a worn pulley. So the dealer is pretty much doin the ol'
" if ya cant convince em...confuse em " routine.
It ain't rocket science!
'Course if yer house has more wheels than yer truck...
" Old age ain't for sissies "