If I understand you correctly, the problem here is that the document has twice as many measures as needed, where the second half of the measures only contains the bassoon part, right?

This means that the problem is, how to select and delete measure stacks, right?

To select a measure stack:

Selection Tool.

Double-click the measure.

To select a region:

Go to one end of the region, and select the measure at that end (via double-click, as described above).

Go to the other end of the region, and Shift-click the measure at that other end.

Now the entire region is selected.

To delete a selected region:

Edit menu > Delete Measure Stack

(note the keyboard shortcut next to the words “Delete Measure Stack”)

Many thanks!
It's a steep learning curve, and I'm finally finding my way around the help.