The gap at the leading edge of the slide where the floor step up occurs, appears to have been fixed.  Tom Johnson Camping World in Concord, NC installed an ARG provided aluminum strip that extends along the entire living area edge of the full wall slide and closed the gap.  We no longer can see daylight at the gap or, on a really bright day, through the carpet covering the slide's leading edge.  Outside air intrusion has also been stopped.

I'm told that the ARG Service Center has a fix for the tile breakage problem, but they need to implement it at the Service Center rather than at a dealership.

Ours was "cured" or at least fixed for now with an adjustment of the slide rollers and the replacment of the tile. The tile had been "fixed" grossly improperly by LaMesa RV in Phoenix. They leveled the underside with dry grout and then placed the tiles on top of it. They used grout to hold the tile in place at the edge. Fleetwood leveled the area underneath properly and glued the tiles back in properly and we have not had a problem since. 

My guess is that as so many of us have had the problem they have tracked the problem down to it's actual starting point and I may have the problem you have. It is too coincidental. I am now out of warranty and I guess will have to hope for the best. 

The latest on the cracked floor tile:

The REV Recreation Group Service Center's (formerly the ARG Service Center)  latest attempt to resolve the cracked floor tile problem has failed.  When a new crew looked at the full wall slide floor during the 6 July 2016 appointment, they said the floor was delaminated, but there were no broken welds in the floor's framework.  They said they re-glued the floor's laminations, added a roller and adjusted the original rollers to better distribute the slide's weight (one roller was said to not be touching the coach's floor).  They also said the tile that was cracking had not been properly grouted and had a void under its center.  They made the repairs, drove over the roughest roads they could find, and extended and retracted the slide a number of times.  The tile didn't crack.  The next day they drove the Expedition to the rain test bay and back, and when they extended the slide the tile was cracked.  I was told that engineers are looking at it again.

So, I don't know what to believe.  The crew that worked on it in June said the slide floor's metal framework had broken welds.  The crew working on it now says that it doesn't.  Both crews said the floor was delaminated.  Adding a roller and moving and adjusting others has been tried before.  It didn't work then and apparently hasn't worked this time.  I don't think Fleetwood (REV Recreation Group) has a clue about why the tiles are breaking.

By the way, the slide floor is covered under the 3 year structural warranty.

We are back from our latest Decatur outing.  The REV Service Center called on 1 August to say they were done with full wall slide adjustments on our 2015 Expedition 38K, and the floor tile had not cracked after numerous extension-retraction cycles.  This time they added three rollers to the full wall slide and moved them so they are more or less evenly spaced, except for the two closest to the bedroom step-up, which are about a foot apart.  They also shimmed the rollers to make certain they touch the floor when the slide is retracted.  There are now a total of eleven rollers on the full wall slide, six under the living area portion and five under the bedroom portion.  The service center also provided Habegger Slide Glides (specialized pads) to put down under the rollers before retracting the slide.  The original intent of the pads was to prevent the steel rollers from scratching the ceramic tile.  I think that in our case, they hope the padding will help ease the pressure from the rollers.  The pads are a pain to put down.  You have to retract the slide enough to raise the leading edge off of the floor, then, on your hands and knees, look under the carpet to locate the rollers and position the pads.  Our final solution to the problems we have experienced may be to trade for some brand other than those built by the REV Recreation Group.

The service center also fixed the gap by the bedroom step-up by installing rubber flaps and a carpeted wood block that abuts the vertical part of the step-up.  We no longer see daylight streaming in when the slide is extended, and we no longer feel a draft when the interior and exterior temperatures differ.