Ive got a very similar situation with my slide floor. I have a 2007 F30RES and bought it during the autumn with it on a pitch, slide was out and all hooked up. We used it 4 weekends before moving it and never noticed any problems but when I tried to bring the slide room in it tilted out at the top and I thought it was going to fall out... Luckily I managed to pull the top of the slide in from the inside and we got it closed up.
Took the unit to a repair shop (Im in the UK by the way, so no dealership to speak of) and the guys there were very knowledgeable, told me they had seen a few like this and that the ply floor had basically come away from the stud walls at the side of the slide room (due to it being left on a pitch for many months with the slide out). Its been in their repair shop waiting its turn for work but the plan is to dry it out thoroughly, inject some sealer, then use long screws to pull that floor up to the wooden batons at the bottom of the side walls. MrMusic, is that what youre showing on your photos?
Ive attached a couple pics which you can see the ply floor sagging out of the bottom of the slide room. The pics werent of that fault particularly as I didnt know I had it at the time...
Im really praying these guys can fix it. It also has a leak on the back wall (not inside the trailer) and so that needs work too. If only I had known what I was looking at when I bought it... We still love it though and really hope it can be repaired!