It does seem as though there should be some end point after the OBS call and the ball is in the circle.
You could have a runner dancing back and forth off first base that most will recognize as a LBR violation.
Heck, the runner could break for second base while F1 is taking her signal. (I guess that is the opposite of a delayed steal.
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If an umpire doesn't call time, what happens if the runner from first leaves early on the next pitch. Do we have an out for leaving early, or are we still protecting that runner from the OBS call??