Metronome and Click Source Bug

I have

1 project, 74 tracks
1 track - very complicated timing at 240 BPM, 4/4 - metronome is a must
1 track - click source
1 Midi Editor open to the complicated track
All tracks EXCEPT the track being edited and the click source track are MUTED
* Metronome ENABLED (at all default settings)
* After Metronome fails to behave consistently, add click source track and "Solo" with Complicated track

On "Play"

Do {
the metronome is intermittent, meaning it either plays, or it doesn't.
the click source track either plays, or it doesn't
} while (swearing loquaciously);


Dell XPS 435T/9000, 24 GB Ram, 3 TB SSD, 2 TB HD, Windows 8.1 Pro (x64), 2 ea Lynx AES16e, 1 ea Aurora 16, 1 ea, cup of Pete's French Roast

EDIT: Additional Insight - I also have a Presonus Faderport. Sometimes I tap my keyboard spacebar to "play", but normally I use my faderport. I've been using Adobe Premiere lately and have gotten into the habit of tapping my spacebar to run a video sequence. I just noticed that the Metronome in Reaper doesn't run when tapping my spacebar, but always runs when hitting play on my Faderport. Bizarre.

EDIT 2: Even more insight: After un-muting the other 72 tracks, I discovered that I heard no audio at all when tapping my spacebar in order to play the track. If I used my Faderport though, it was fine. So I loaded another project with 20 tracks. Not only are there fewer tracks, but there are no audio files in this project (not sure this matters). The metronome and audio are fine, regardless of whether I use my keyboard spacebar or the faderport to play.