There can also be errors printed between header and score. In this case there can be pagebreak after header. Actually nopagebreak is for normal counterpoints without errors. Any error can actually disable nopagebreak. Another solution is always to keep errors between header and score unbreakable. This can have a side effect of pagebreaking between score parts if score is long and high enough.
Solution:
Make errors font smaller to avoid side effects
If there are less than 5 voices and 5 errors, do not break errors
On the other hand, most important is to have score with mistakes on the same page. From this point of view nonbreaking is not important.
Another important point to mention is that in Composer tools usually there is only one counterpoint.
There can also be errors printed between header and score. In this case there can be pagebreak after header. Actually nopagebreak is for normal counterpoints without errors. Any error can actually disable nopagebreak. Another solution is always to keep errors between header and score unbreakable. This can have a side effect of pagebreaking between score parts if score is long and high enough.
Solution:
On the other hand, most important is to have score with mistakes on the same page. From this point of view nonbreaking is not important.
Another important point to mention is that in Composer tools usually there is only one counterpoint.