I have occasionally had this kind of thing happen. I don't have any good answer for preventing it for certain.
One thing I do is refresh the schedule page after I finish setting up an away series. Sometimes, for some reason, a selection doesn't "take" on that screen.
There is an off chance that you inadvertantly failed to submit the saved settings for the game, or that the transmission was interrupted at that point.
I'm not saying the glitch was your "human error," but in rechecking my submission I do occasionally find the selection hasn't been recorded.
Or...maybe the robot just hates you. I sometimes think this is true, especially when in series like the one I had recently where low-rated pitchers threw like Cy Young and Randy Johnson against my team.

Dave N