My 10" DW717 also did not have the smoothest slide action when I got it in 2008. I found though, that a large portion of the stiction originated from the 6 dust seals around the slide bearing/bushings. When I loosened the plates on the front and back of the trunnion assembly (where the slide bearings are) and temporarily slid 4 of the dust seals up the rails away from the trunion (the other 2 seals are fixed to the linear bearing assembly), I noticed that the sliding action loosened up considerably. I also own an old Craftsman Professional 8 1/2" sliding compound mitre saw that slides like butter, but it does not have any additional dust seals around the bearings meaning less durability. My DW717 did smooth out with use, but after the warranty period I decided that i could likely improve the sliding action further. The porous bronze bushings in the right hand side of the trunnion come from the factory impregnated with some oil, but I found them to be on the dry side. I experimented with a few lubricants including light greases and different grades of oil and found that a lightweight oil (10W or ISO 32) has worked the best. I also added several drops of oil to the inside of the linear bearing by removing the rails, since I also found very little lubrication in there. As for the 4 mm set screw, I set it so there is maybe a few thousanths of an inch play, but no tighter. The saw is much smoother now than it ever was. The additional oil has not only smoothed out the bearing/bushing action but also eliminates most of the stiction from the dust seals. I wouldn't recommend tinkering with a brand new saw on warranty, nor should you have to, but it does appear that the issue you are experiencing may not necessarily be with the bearing but rather a combination of tight seals, break in period, and inconsistent factory lubrication between batches.