The cabin sole covering is loose in the area just behind the compression post and between the bunkboards. When compressed this covering seems to be in contact with loose aterial; is this the concrete ballast come loose? Any suggestions on how to correct the loose covering and/or the material beneath?
Yes, it's just loose concrete. If it's not too bad, just cover it up with outdoor carpeting. A small amount of removed "gravel" is no big deal. If it's real loose with a lot of gravel, about the only thing you do is to remove and chip out any suspect concrete and lay new. Sounds like it may have had long term moisture in there?