Update:
I found a YouTube video (Line 6 M13 scene for worship) by Blake Fischer that has a downloadable SysEx file, which loads perfectly as a scene named "P-Dub!". So I now know 100%, that given a good file, my midi setup for loading back SysEx files works! However, when I export that same file from the M13 as a scene dump, to either my PC or new MacBook Pro, do a factory reset and then reload my saved SysEx file, nothing happens. The file seems to be corrupt.
For the "P-Dub!" scene in SysEx Librarian, it shows the Manufacturer as "Line 6 (Fast For" and then it gets truncated with #.. showing 16. My saved file of the same scene shows up as Various in Manufacturer and 31 in #..
Does anyone have any idea what is causing this apparent MIDI output corruption and whether it can be resolved?