If you like the second dealer, take the car back to them and give them
specific instructions about what is necessary to make the condition occur,
or, even better, take one of their technicians on a drive and point it out
to him (if that's possible). You should be aware that if they need to
drive the car for an extended period of time, that you'll probably need to
make some sacrifices. Hyundai won't pay them for extended test drives.
One of the things we do is to drive the customer's car home overnight
(with the customer's permission, of course) in order to make a
significantly longer test drive. If this is okay with you, make it a
point to tell them it's okay when you drop off the car. That way, they'll
know you really want them to duplicate the problem and are willing to take
some of the steps necessary for them to do so.