Is it a bad sign? I think it's a warning that's worth looking into, but I also think it's bound to happen.
When people submit any kind of feedback to me, I try to filter it into three buckets:
- Feature Requests
Bugs are when something obviously doesn't work the way you would expect, nor the way the user would expect. Like, it asked me for my name, I entered "Scott", hit enter, and it said, "Hi Joe!"
This is like "I know we never talked about this, but can the program infer from my mouse gestures that I'm left-handed and move the OK button to the left side of the screen?" This is when the current behaviour matches both your and the user's expectations, but they want to change the expectation.
This is when you would expect one outcome from a scenario, but the user expects a different outcome. Sometimes this becomes a feature request, if they just haven't communicated their expectations, but they thought they did. Sometimes this becomes a bug if your expectation is proven to be wrong.
However, many times you have knowledge that the user doesn't have. What if they said, "On this screen, I can add a record for myself twice with the same first and last name! That's obviously a bug!" Your response might be, "There are lots of people in the world with the same first and last name, so we don't require that combination to be unique. We have a cleanup task that runs at night and emails a Possible Duplicates Report to customer service when it thinks it detects a duplicate with a similar name and address, and asks them to check it manually."
So you should read every bug report, but most complex systems are going to have bug reports that are really just feature requests, or possibly a mis-communication of the requirements. Not understanding the underlying complexity of the real world is probably the biggest source of these issues.