I have a 12 bar drum riff I'm working on but when I listen, the transport plays back 17 bars. That's 12 with drums and 5 with nothing. I am using 6 outs for the drums.
 
I've looked at the event manager for each track and can't find anything, in any track, after the 12 bars. What/where do you think something is hiding?

Audio or MIDI?

Automation?

Excuse brevity, replying on phone.

Is there anything on any track anywhere except the 5 bars of drums? If another track somewhere is 17 bars, even if it is empty, then the 5 bar drum track will include enough silence to reach the end of the project.

Only 1 midi track in the project and nothing is visible past the 12 bars. I'm looking at all note and event data and have checked the take lanes as well.

Things to check:
 
Tempo changes
Meter/Key changes
Automation nodes
Hidden tracks
Archived tracks
Bus automation
 
Where does the Now time go when you hit ctrl + end?

When I press ctrl+end the now time moves to measure 14 and I can find nothing there. So I have a 12 bar midi drum track but Sonar thinks there's 14 bars and plays for 17 bars. Eventually I will figure this out but I have to say it seems way too hard. I could start a new project and be in business in 30 seconds but I'm trying to figure it out in case this happens with a real project that I don't want to walk away from.

There was a volume envelope that extended beyond the end of the track. I have no idea how it got there because I really never touch things like that when I'm just building tracks. Very strange.

It is pretty easy to hit the automation lanes button instead of the take lanes button in the track header. This creates a volume envelop. It might be worth a FR to suppress automatic creation of a volume envelops.

So if I understand you, just looking at the automation lane contents to see if there's anything there can create an envelope? I had a tempo change get inserted early on and was looking for it. I looked everywhere, including automation lanes.

I believe so, try it.