There are three trombones playing a glissando
In page view the gliss. is not being displayed across frames in the condensed staff
But it’s displayed correctly in the same frame
And surprisingly it’s also being displayed correctly with a slur
It is a known issue. See Glissando/portamento in div disappear at system breaks - #2 by dspreadbury
Thank you for pointing out. I searched the forum but apparently with the wrong keywords,