It doesn't provide a DWG, and I've never seen it in R2012 with daily use in our files or outside shared files: so my guess is you got something else going on and you are only seeing this "symptom", which is not the cause.
If you've got a DWG that does this, post it (remove any sensitive info of course): we all have 2012 here and I'd love to dissect this in more detail.
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