Poor performance with very large track counts and Mackie Control surface

[tack]

While testing out a project with about 1000 tracks, I noticed that selecting tracks (by mouse click) was very sluggish. The lower track counts select quickly, but it was increasingly sluggish as I clicked on the higher track counts, suggesting some kind of O(n) behaviour with respect to track number.

I tried this project out on a fresh install of Reaper and it was very snappy. After quite a bit of trial and error, I finally honed in on the cause of the sluggishness: my main install has a Mackie control Universal surface configured.

Removing the Mackie Control Universal surface configuration and things immediately improved.

Further investigating, and I see that each time I click a track, Reaper sends about 5000 MIDI events to the Mackie control surface MIDI output device. Is that expected?