When I set up loop recording in comping mode, it works perfectly the first time through.  All takes are recorded new take lanes, the previous takes muted as the next one records, etc.  However, if I stop loop recording then decide to go back and record additional takes, Sonar no longer creates new take lanes for each consecutive take.  It'll store all new takes in a single take lane, so then I need to go back, manually create new take lanes, then drag/drop individual clips from the cluttered take lane into the new, empty ones I created.
My workaround is to bypass loop recording altogether and just manually start/stop recording, create a new take lane, record enable and solo it, then record again.  It's cumbersome but manageable when recording another person's vocals, but when I'm recording my own vox, it's a major time suck to have to manually create a new take lane each time I want to record a new take.
 
Am I making some sort of dumb mistake, or is this a known bug in Sonar?  I haven't seen anything about it on the forums, which is strange because I imagine loop recording is a pretty common practice, especially when paired with the comping feature.
 
Thoughts?

Which version of SONAR are you using?   I believe starting with X3 new clips can't occupy the same space as other clips on the same lane.   At least not under normal circumstances...  
 

Sonar Platinum actually. The particular project I'm working on was created in X3 though.

Make sure you have Create New Lanes on Overlap checked in Record preferences. This setting is largely superfluous now that SONAR doesn't normally allow same-lane overlaps, but there are some situations - like the one you've encountered - in which you can still get overlaps if this option isn't checked.
 
EDIT: That said, I just tried to reproduce this with a new project started in Platinum build 37 with Create New Lanes unchecked, and could not. So what your encountering could be a holdover from a project started in an earlier release.

Yep, that box was indeed checked, but you must be right.  I kept the same settings and started a new project in Platinum (build 37 as well), loop-recorded a handful of takes, stopped, auditioned some takes, then went back in and recorded more takes, and it worked as expected, no overlap.
 
As you said, the issue must be a holdover from X3.  Kind of a pain because I have several in-progress projects that were created in X3, but at least I have a workaround and know that any fresh projects created in Platinum will loop record as expected.
 
Thanks for the feedback!