There is no way to know if that is a bug. I understand you want a reason, but addons can not control that or break that or people would use that for nefarious and dubious acts. So you can eliminate the possibility of a mod. However, nobody is going to have that kind of information not even the developer that normally talks to us about the UI and guild history, for example.
The customer service ticket and the post on the official forums is best.
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