Steps to reproduce:
Record four chords in a DAW with midi export, using four voices each chord (in studio one for example).
At the beginning of chord 1, make one note very short like 1/16th, an then copy the same note after the now shortened note to 3/16th position.
Export the event to a midi file and drag that file to renoise.
The note on 3/16th position is placed in front of a totally different note, so stopping the wrong note.
The note should be placed on a column where a note-off already appeared or no note at all did play so far.