In a situation with many midi tracks some of which have midi events within a desired time range and others do not have midi events within the same time range, the selection range can be changed in an unfortunate way.    
 
Select a group of tracks, select a time range, perform an operation on the selection.   Could be any operation: run a cal script, transpose, change length ... 
 
Now, an unwary user might decide to do another operation on an extension of the time range.    BUT:  the selection is no longer the same.    Those tracks which had no events in the originally selected range have been taken out of the select group ... so your new operation will NOT be done on those tracks, even if they in fact have some events in the newly selected range.    
 
I'm sure some of the sonar fans will say, well why don't you just look at your selection and notice that it needs to be done again ... but, real life cases, often the tracks that got dropped will not be visible .. they are not currently in view in track view. 
 
If this can be said better, please help do so.
 
Another, related, selection bug:   do as above, then UNDO.   The selection is changed.  Not only the tracks but the time range is also changed. 

Every good morning starts like this... but I think I remember noticing stuff like this. I think of it as unexpected behavior. Then I have no moral obligation to find the right spot to report it.
 
Carry on William (I love to call ya Bill)

You need to give steps to reproduce, and explain what you mean by terms like "extend" the time range. Do you mean holding shift and clicking elsewhere in the timeline? Drawing a new region? Slip-editing a clip to make it longer, which automatically extends a region?
 
I did what it appears you said, although one can never be sure...
 
1. Selected all MIDI tracks, including one without data, and click+dragged a region in the timeline.
2. Transposed. The region changed slightly because it fell over part of a note. After transposing that note, of course the entire note became part of the selection.
3. The track without data was deleselected, the other tracks remained selected.
4. I clicked further down the timeline to extend the region length so it would include a MIDI clip that was later in the deselected track.
5. The track with the MIDI clip was automatically selected, which is what I would expect.
6. If I slip-edited a clip past the selected region, the region changed to accommodate it.
 
How is this a bug? If you truly have found a bug, and not just behavior that's not as you wish it to be, you need to give steps to reproduce that "bug."

Anderton
3. The track without data was deleselected, the other tracks remained selected.

My interpretation of OP, that is what is called a bug. The rest is the explanation why that is a bug. So, you could reproduce it but you do not agree that is a bug (which was also "predicted" in the OP).
 
It looks like we need some voting system to decide either something is a bug since some bugs are subjective

If there's nothing to select, it's logical that SONAR would de-select it -- but that's not really the point, because it doesn't remain de-selected if you extend the range so that there is something to select. SONAR automatically re-selects that track. Why is that a bug?
 
You could just as easily say it would be a bug if SONAR keeps a track selected when there's nothing to select. A typical definition of a bug is like what Techopedia says - "a problem causing a program to crash or produce invalid output." Based on the limited amount of information given to reproduce, I'm not seeing a crash or an invalid output.

So, in between mouse selection I just press Del key
 
Now imagine you try to transpose 20 selected tracks (but not ALL, you do not want transpose Drums), selecting time periods and transposing by required amount. And some of these tracks has periods without MIDI notes...

It is not that there is nothing to "select," but rather nothing to "process." Using timeline as X and highlighted tracks as Y, clip regions with no data in the time selection (even if other areas of the clip do have data) will have the entire track deselected after running a process. If the user had to cherry pick tracks to select them in the first place (most likely the OP's situation), now they have to do it again. A selection should be able to be left intact; if there is nothing to process, what harm is that doing SONAR?

FYI - SONAR does not automatically re-select tracks in the above scenario, and why should it? It has already deselected them and not remembered doing so; and the user should be (de)selecting tracks, not SONAR.
 
[I know, I know... workaround and stick them all in a folder after the initial selection... but wait... how does the user then put them back where they were?]

mettelus
FYI - SONAR does not automatically re-select tracks in the above scenario, and why should it? 

It does in the scenario I described, which was based on WC saying he extended the selection. He didn't say he made a new selection, like azslow3 did above. This is why it's so frustrating to have someone claim there's a problem but not provide enough information for me to reproduce, so I can understand what's going on and hopefully come up with a solution.

Apropos folder...

azslow3
Apropos folder...

Now, THAT for sure is a bug.