uTool says “error” when exporting *any* multitrack song with MIDI

Some more information:

After I have completed a an export, close uTool and reopened it at the export function, I see the files listed in the Target Content tab; some say “Quick Export” some say “Error”. For those that say “Error”, if I hover over them I see some information about the songs and it appears that uTool doesn’t recognise the MIDI files, even though it successfully exported them already.