I can confirm, volume parameters are broken for certain MIDI files. I will allow you to select between Volume Actions, Volume Parameters, and No Volume in the next update. For now, there is a workaround:
Go to MIDI2TDW\MIDI2TDW_Data\StreamingAssets\config\settings.json
and change doVolumeParameters
from 1 to 0.
I apologize for the inconvenience.