Hmm, OK, here we go ...
... Big pic:
https://i.imgur.com/tqFwz4u.png
This shows
(a) the MIDI file imported into Reaper
(b) the MIDI file imported into XT2
(c) the MIDI file exported from XT2 and imported into Reaper.
What I see
(a) the second F#1, the first D#1 and the first F1 are all 35 ticks early in the MIDI file; they are the lower notes and it does not seem to be coincidence- was there something special in the Notion notation about them?
(b) the second F#1 thus overlaps the first and causes it to be truncated,
(c) and the second F#1 is truncated by the Note Off for the first F#1 ?
(d) in Reaper, the tick values are all 1/5th of what they should be
(Bug) - e.g. the first F#1 shows a numeric length of 89 ticks; in XT2 it is 445 ticks
(e) the tick values in the timeline are similarly incorrect, see the screenshot below,
(f) after exporting the clip from XT2 and importing it into Reaper, whatever was messing up the tick values is no longer present (see the 'correct' tick values in the second Event List, above), but the second C#2 now has a length of 0.
(g) at the end of the clip, there seems to be an F#1 with a length of -1, this could be messing things up,
(h) the MIDI file has a tempo event in it (90 bpm) - that could be messing things up? It shouldn't, but ...
... Big pic:
https://i.imgur.com/FQaTWM4.png