Can't split a secondary beam

please view the attached picture-
I want to split the group in the lower bar, as I did in the upper bar, but for some reason, it doesn’t react.

How did you try to split the 16th beam?
I replicated your example and managed to split the beam in Engrave Mode, properties panel, split secondary beam.


via right click: split secondary beam.
I’m attaching the project, it’s in the last bar of flow 2:
Seu_Zimra.rar (274 KB)

After unpacking your file, Dorico cannot open the file. I get an error massage.