First, let me state clearly that this is not to do with the AI spamming bounty. It is annoying, but I'm resigned to that fact for the moment

However, one thing I have found is that sometimes I get an alert about the bounty being raised on faction X
The message goes something like this:
The bounty on faction X has been raised by 500 to 0.
I've only ever seen it with the bounty being raised by 500. Anyone else noticed this?