We have a 2016 Wildcat Maxx 262 RGX and the same thing is happening to our floor. As you have been doing, we carefully sweep the floor before we bring in the slide because we know that small rocks are the main culprit.
As the slide starts to come in the slide floor tips up a bit and I'm hoping I can get my fingers under it and look for any screws, nails, or staples that might be hanging down causing damage.
Please let me know what you find and I'll do the same. We've used brown paint in several areas to hide the damage but the real answer is to stop it from happening in the first place.
2016 Wildcat Maxx 262RGX
2012 Ford F350 6.7L PSD