Sometimes I think that the challenges which don't involve teammates should have the bases empty for each at-bat.
I played a challenge a bit ago which requires the player to tally three extra-base hits in a single game. After a few tries, I finally got off to a good start, hitting a home run in each of my first two PAs. In the 3rd PA, I was walked intentionally. Okay, annoying... but it fit within the logic of the game.
In the 4th and final PA, there was a runner on first, and I sent a high deep drive to right-center. When the ball hit the warning track I was about 10 feet from reaching 2nd base and completion of the challenge. The runner ahead of me retreated to 2nd instead of going to 3rd and just like that, challenge over, failed.