Home splitting at marriage wall

[Kathy]

I own a 2000 Redmond that was set on a foundation three years ago. I have been observing the marriage wall and it seems that the home is not set properly. The carpeting is lifting at the marriage wall and you can see the wall coming apart by the batting strips over the section where the two halves are joined.

This is private rented property.

I've also noticed, when you walk over the marriage wall section, you can actually feel the heat through the floor where the heating vents meet at the marriage wall. I did tell the Dealer about this the first year after the home was set, but he said it was nothing to worry about.

Who is responsible to repair this? I believe the warranty ran out, but the home may not have been set properly to begin with. This is not a new foundation. There was an existing home here before we took over the property. There is only a small crawl space under the home because, the Zoning officer made the land owner fill in the foundation due to cracks in the foundation wall. When they filled in the foundation, they put in cement piers. Unfortunately they filled in the foundation 3/4 of the way up, so the crawl space is limited. There is no way I can go under there to check it out and see just how bod it looks. I am scared to death of enclosed places and this is really a small crawl space. I know this because they had a hard time setting the home because of the 3/4 fill in.

Any suggestions would be greatly appreciated.

What could happen if this continues to split apart? How will I know if my determination is correct just by my observations?

Is the Dealer and set crew responsible, or do I have to pay someone to come in and repair this mess?
Thank you for your time.
Kathy