I have a piece in which there are two percussionists, each playing both a mallet and a percussion set-up which is notated in the score on a 5-line staff.
In editing the part lay-outs, one of the parts looks just like the score with the 5-line staff throughout for the mallet and the unpitched set-up, but the other one keeps switching back and forth between the 5 line mallet staff and 7 widely spaced percussion lines.
Why would this be happening when I set up both percussionists the same way?
It sounds like your second percussionist has instrument changes between a pitched instrument and a percussion kit, but the percussion kit is set to use the grid presentation type in the part layout.
You can change the kit’s presentation type to use the 5-line staff in the 2nd percussionist’s part layout instead.