Within a few months of moving in we started noticing a gap developing between the baseboard trim and the wall going up the stairway to the second floor. Several of our neighbors that had been in their houses longer told us they had experienced the same problem so I was expecting it to happen in ours too. Once we turned the heat on in late October it only accelerated the rate of separation to the point where it was two-thirds of the way up the stairs and relatively wide in spots. When I spoke with the service manager about it he said he sees it in 99% of the homes they build and can't be prevented. It's caused by the water based latex caulking drying out and is just one of those things that happens. (Silicone caulk can't be used because it can't be painted over.)
For whatever reason the only spot we've had this happen is the staircase and on the side against the exterior wall at that. Our original plan had been to get it fixed at the ten month review (which for us is only two months away) but it reached the point where it looked awful and with having family over at Christmas we didn't want to have such an eyesore sticking out.
Fixing it was easy enough. The contractor that showed up to do the repair used a nail gun to pop a few nails in the trim at the widest spots and followed it up with a bead of caulk. It looks good now with barely any hint that something has been done to it. Now that I've seen how it's done it should be fairly simple to do it myself should the need arise again after we're out of the one year warranty.