If you have another notation program, such as MuseScore (which is free), you might like to try importing the MIDI file into that and see what sort of result you get, then export it either as a musicxml file or a MIDI file and try opening the exported file in Dorico. Given that the original file is behaving unexpectedly with Dorico, it is highly likely that you will need to do some tidying up of the note values before exporting it from the other program.
Thanks, @dspreadbury - is that a specific limitation of Dorico… or is it in general, a MIDI file should include note off events to achieve expected results per typical implementations?
Sometimes MIDI running status is used to save space. Instead of a note off a note on with velocity 0 is used. That doesn’t seem to be the case here though.
I’ve seen a lot of MIDI files over the years, but MIDI files that only define “note on” and never “note off” are unusual, in my experience. How is the importing application supposed to guess how long the notes are if the MIDI file doesn’t specify?
Obviously if you’re playing back percussive sounds, you don’t need the “note off” from the playback point of view because the note will naturally decay, but if you want to notate it, I would think “note off” events are pretty essential!
Moreover, the lack of note-off events implies every note struck is held until the end, including duplicates! Even if you’re playing non-sustaining samples, sooner or later that will exceed the polyphonic capacity of any synth.