The slide in mine goes under the couch and doesn't hit. I guess it's possible that your table side slide rises up higher than mine and it causes it to hit the couch. You could either try getting the slide adjusted, or put a block of some sort under the couch to raise it up a little. I did have to have all three of my slides adjusted when I bought it.
We had the same problem. The wood that the castors were on were just stapled on to the couch frame. We put a better piece of wood there, screwed it in than put the castors back on. It raised that end of the couch up just enough so it would not catch on the floor but not enough to notice a difference in the couch to look any higher. Works fine now.