I have a 2011 378 and my main slide had the same problem, wood chipped under the edge, also the entertainment slide was out of adjustment. The slide adjustment is a pretty quick fix as this is a dual ram system rather than a one ram and a cog gear system as some units use.
I found that the rub on the edge of the main slide was not caused by the slide itself, it occurred because the unit was not level using the auto-level system. The slide is a big box sitting in a big hole, both need to be square. When out of level the chassis twiks the slide hole and it creates a jam that the hydraulics over power causing the rub. I did a recalibration of the auto level, then repaired the exposed wood with JB weld. No further problems.
Marclaw15 asked if the underside of the slides looked the same, no, the bedroom slide has a fiberglass underside, the other slides are OSB covered in a dark colored protective coating. The slide ends are screwed through this coating leaving the "holes". This also leaves the raw wood in the screw holes exposed to the elements. I have filled all of those on my unit. Filled with JB Weld, then put packing tape over the filled area until it cures, leaves a nice slick repair when the tape is removed.
JimF, CWO, US Army Ret, 100% DAV
2011 Georgetown 378TS
2008 Dodge Caliber Toad