OK, I found what causes the gap as shown in the picture. I had the conduit laying in the rollers and they were tight against the rail. As soon as I tighten the conduit clamp, the opposite roller shifts causing the gap. I can tighten the one on the gap side without any issues. It appears that the clamp might sit a little skewed on the roller and tightening the screws causes the shift. I shortened up this dimension by an inch so it is not quite as pronounced. Looks like I just need to sand the saddle a bit to prevent this.