As requested: A Forest - The Cure.zip (68.5 KB)
Contains three versions of the exported .sng files and the .mid files.
I can replicate the symptoms in Silicon macOS 15.2b, Chrome as well as Intel macOS 10.15.7, Chrome.
The process works as expected with .mid exports from the default content beats.
Thinking that this could be attributable somehow to my work methodology, I tested my observation with an OPB provided by another user. Same results. Here’s the files for that song as well.
The resulting Export to MIDI of OPB songs seems to be fewer than 7 measures.