1. By mistake, I dragged a soft synth midi track (edit : dragged the midi clip) down to the blank area, thus creating a new midi track automatically.
2. When that happen, one will correct the mistake by dragging the midi back to it's original soft synth track.
3. And proceed to delete the newly created midi track.
 
Now, when you do step 3, the actual soft synth midi track is also deleted at the same time.
 
This bug will not happen if your first move the timeline before deleting the new midi track.

I'd just undo at step 2.
Anyway, it's an interesting behavior. I wish it could happen to Take Lanes as well (i.e. automatic deletion of a lane).

Further test, I found the source of the problem. After moving the clip back to it's original track, the clip is still highlighted / selected - which is the same effect of the track being selected as well.
 
When this happens, deleting another track, will make the upper selected clip's track to be deleted as well. Moving the timeline will de-select the clip, thus only the new track is deleted.
 
This leads to the next question. When I manually select multiple tracks to be deleted, the Delete Track option will report the number of tracks to be deleted, thus one will not make mistake.
 
However, by doing the combo steps, Delete Track will not report the number of tracks to be deleted.

Sounds like a bug.  I would report it.
 
Bob Bone
 

Please leave the issue number here and keep us updated. Thanks.

I'm not sure it is a bug, it is normal behaviour for a track to be still selected after it has been moved. If you had selected the track to be deleted after the move, it would have deselected the moved track and would not have been deleted. All other selection edits I know of work in this way.

Ah, I misread the original post, didn't I? I now understand the issue. But this isn't a bug. I'd submit a feature request.
 
My similar issue: http://forum.cakewalk.com...angeable-m2937905.aspx

I was thinking the incorrect number of tracks to be deleted was a bug, since as I understand it they are both still selected and the count is off.
 
Bob Bone
 

Good point, Bob. It's a bug. 
I think Sonar should change the track selection behavior, though. I mean, if you right-click on a non-selected track, it should be selected and all other tracks should be deselected.

I've been caught by this many times. As long as you catch it soon enough, ctrl+Z is your friend.
 
Once I did NOT catch it soon enough and had to undo a 1/2 hrs. worth of work to get the track back. ugh!