Optimising flow across pages

[charles_piano]

It could be one of the situations described here by Daniel:

„Resolve the collision..” strange behavior

The problem here is that Dorico does not know exactly how much vertical space the music is going to occupy until it has cast it off, but it cannot know exactly how to cast it off until it knows the height of the music, so this is an inherently circular problem. When the 'Automatically resolve collisions between adjacent staves and systems’ option is on, then Dorico makes an estimate of what it thinks the height of the system(s) is likely to be prior to casting it off, so that it can decide when…

In your case, you can either increase a bit the inter-system gap (I tried with 10, it works), or just insert a frame break at the begining of the last system p. 2.