Specific SVG file cut when inserted into another software

Dear all,

I am a music engraver and I am working on a complex contemporary work which needs a lot of vector drawing for special playing techniques and other non-standard notational elements.

So far, everything has been smooth sailing but today I have stumbled upon something that worked until 5 minutes before and is not working now. 

The graphics are created in Illustrator and then exported as SVG to be placed in the software Avid Sibelius (which supports only SVG as vector format). Sometimes, though, I need to export the SVG from Sibelius or Dorico, two music notation software, clean it in Illustrator, re-export it in up to SVG 1.2 Tiny standard (the maximum that the QT framework appears to support), and re-import it again in Sibelius.

Attached below you will find three files. The "4-b1_3-DB" and "4-b5_7-DB" ones work flawlessly. They have been exported from Steinberg Dorico through a feature called Graphical Slices which lets you draw a rectangle around something and export just that in the desired format. I exported them, opened them in Illustrator, File > Save As, selected SVG, in the settings states 4 as decimal places, 1.2 Tiny as standard, unchecked Responsive and hit Save. In Sibelius, the import has been perfect!

Now, could you please help me understand why the file "4-b32-Vc" is not behaving as well as the other two? Upon opening it in Illustrator I can see the whole staff (5 horizontal lines protruding at each side of the figure) and, even if I fix it to how I want it, I get the error "Transforms are not expanded".

I have tried everything I know to fix this but I am now completely stuck because, when I import this new file into Sibelius, it is missing its bottom portion, and looks like this:

 Any help would be more than appreciated!

PS: of course, I could create a new document in Illustrator, manually draw everything and export but... I believe that if it worked once, it should always work, assuming the material and methods are the same.

Thank you!