I think the issue is the way you are doing it.
MSLB will put multiple selections on a line which is hard to parse.
I would recommend ditching the MSLB and using a repeating section with a dropdown in place of it.
Then, you can just point your second dropdown at the main data source and it will list the software titles that were chosen in the dropdowns in the repeating section.
Hopefully this makes some sense. If not, please email me. I can show you an example in an online meeting.