Why do some pairs score 101% on some boards?

This is a multi-session event, and you seem to have added a few pairs in the 2nd session. That combination means that Magic uses Neuberg’s formula in session 2 with the same top as in session 1, which is then lower than normal.

Normally, when Neuberg’s formula is used, there are less results on a board. With more results, the effect of the formula is that the top can exceed 100%.

There is a setting in Contest menu > Properties > Scoring and the Matchpoints (more) tab where you can enter a specific top. For 10 tables you should enter 18.

Since you have already created both sessions, you need to make the appropriate change in both sessions. Now there will be other matchpoints in both sessions, but the ranking should stay the same unless Neuberg’s formula in session 1 causes any strange behaviour.