In my full band score, about half way thru doing parts in score order, on the second page of the parts, there started to be a big gap between 2 staves in the middle of page. I just moved them manually. But the problem got worse, gap got bigger as I did more parts. By Timp, the staves were all on top of each other, some at the top, some at the bottom, difficult to pry apart manually, but possible. In Perc 1, same problem, but m56 disappeared in the part. After playing with system breaks and frame breaks, got that back. And, after manually moving staves to appropriate positions, as soon as I enter a system break, they all jump back into one overlapping pile. I think the vertical spacing settings in Layout are correct. Please help! Thank you!
Link to the file in Drop Box:
https://www.dropbox.com/s/zpt3ou7hwzff1zz/Dorico%20J14B%202017-10-17%20perc%20part%20staff%20spacing%20problem.dorico?dl=0