Hi Mat.
You are a very knowledgable, tech savvy guy (I am not) , I'm sure you know this already so forgive me for jumping in here but others may find the following useful.
Powertracks Pro Audio has a very useful feature called Event List . Import your midi file into Powertracks
then go to the menu bar/Windows and scroll down to #9 Event List or simply press F2 on your keyboard.
Firstly delete those invasive Sysex files (these may be the cause of your problem Mat). They are coloured black and usually are at the top of the list.
(more directed to all)
Here in the event list you can take back control of your imported midi file.
CC's are coloured purple.Delete these. They control panning,volume,chorus,reverb etc. The only CC's that are good to keep
are the PedalCtrls which control pedal on off (mainly sustain) so try not to delete those.
Midi notes are coloured Blue so don't delete those.
Now when you import the treated midi file into your DAW of choice you will have complete mixing control.
Kudos to Powertracks for having this very useful capability.
Mat , when I import either a type 0 and type 1 MIDI file into my Daw (Mixcraft) , they remain silent until
I actually assign each track a voice within my Daw. Could that be a clue given that Corrillion is a Midi File Player.
Have you tried asking the good folk at The MIDI Association <info@midi.org>
midi.org
https://midi.org/community (forum)
good luck.