Looks like the slide floor is bowing from rollers in center out of adjustment or shimmed by someone.
Some slide floors were known to bow after manufacture, may want to give Newmar a call.
The bolts you are talking about maybe the stop bolts for travel of slide out and in which are the stop rods with double nuts to lock for distance traveled.
Pictures of slide rods.
That link is incorrect for slide adjustment Its my version, correct info is in this
old slide spec, in trouble section,
page 7, for adjusting slides.
Your slide floor is bowed and adjusting will not help floor needs reinforcement, to make flat.