I think I found the culprit: it is the source .mid files you're using that are troublesome or/and not quite well-formed if not simply disfunctional; at least for the Qtractor's already 2 decade old MIDI file parser, sequencer and renderer...
the root cause and most probably the problem seems to be some of your .mid files are showing contiguous sequences of note-on, note-off and then note-on events at the exact same time (ie. zero delta-time); although this might work fine for external/outboard MIDI instruments, it doesn't at all for internal ones, that being plugins, no matter their type (LV2, VST or else).
for example: "02 - Freebee.mid", track/channels 3 and 4 (might be others): most note events are simply bad because of the above reason--if you just eliminate or strip those note events from the file--note events with zero duration--they will all start playing fine (in plugins).
so it seems it's a bug in the original MIDI files and not Qtractor per se
although Qtractor could cope with that alright, it must be here said that those zero-duration-note-events are actually and utterly non-sense and should be sanitized at the source.
I think I found the culprit: it is the source .mid files you're using that are troublesome or/and not quite well-formed if not simply disfunctional; at least for the Qtractor's already 2 decade old MIDI file parser, sequencer and renderer...
the root cause and most probably the problem seems to be some of your .mid files are showing contiguous sequences of note-on, note-off and then note-on events at the exact same time (ie. zero delta-time); although this might work fine for external/outboard MIDI instruments, it doesn't at all for internal ones, that being plugins, no matter their type (LV2, VST or else).
for example: "02 - Freebee.mid", track/channels 3 and 4 (might be others): most note events are simply bad because of the above reason--if you just eliminate or strip those note events from the file--note events with zero duration--they will all start playing fine (in plugins).
so it seems it's a bug in the original MIDI files and not Qtractor per se
although Qtractor could cope with that alright, it must be here said that those zero-duration-note-events are actually and utterly non-sense and should be sanitized at the source.
cheers, hth.