The Tracer manual says, "The Tracer-A series is a positive ground controller. Any positive connection of solar, load or battery can be earth grounded as required."
Earth grounded is not what happens in an RV installation.
My old PWM controller manual has " a common positive ground" and the diagram on page 6 here shows to "ground" the positive battery post if you do. In fact, I had the usual battery negative "ground" to the RV frame and the controller's output to battery pos and neg as usual, and it all worked no problem. (I had the plain version not the R one , but all same really)
http://www.epsolarpv.com/en/uploads/news/201310/1382336207652695.pdf