I just tried it with a fresh portable Reaper v4.602.
- Install + open Reaper
- Preferences -> Editing behavior -> MIDI Editor:
1) Set "One MIDI editor per:" to "Project
2) Set "Behavior for..." to "Open all MIDI in the project"
- Apply changes
- create four tracks (name "1" through "4")
- create one MIDI item on each track
- doubleclick on the item on track "2":
(- not necessary, but easier to follow: make track list visible in editor)
=> Editor opens with item on track "3" active"
- doubleclick on the item on track "3":
=> Editor changes active item to the one on track "2"
EDIT: When I add a track + item between "2" and "3", only track "2" opens with the wrong one (the one I added), the others seem to work right. Adding yet another one made them all mix up but the first one. No rhyme to it, but definitely something ending with "...ug"