hairpins in above ossia staff collide with main staff

[Frédéric Bron]

Hi folks,

I created a 21 page score with only one staff but at some place, an
ossia staff appears above the main staff. Everything was fine up to
the point where I needed to move the bar number engraver from the
score context to the staff context because I wanted the bar numbers to
be below text spanners. After doing this, hairpins of the ossia staff
started to collide with the below staff.
I noticed that if I do not use "\override VerticalAlignment
#'max-stretch = #ly:align-interface::calc-max-stretch" no collision
arises.
Also it works fine if I use "\override VerticalAxisGroup
#'minimum-Y-extent = #'(-5 . 5)" in the main staff context but with
(-4 . 4) it is awfull. Why such a yield effect?
Does anyone understand anything? I tried to make the example minimum
so I put some \break and \noBreak to mimic the original 21 page score.

Frédéric

hairpin-staff-collision.ly
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