Is it bad to have a BUG in our published code? Not at all.
Is it bad to have a REPETITIVE BUG in our published code? Absolutely!
The thing is people usually forget the intention of automatic tests. Those are not to prove we have no more bugs. Those are here to help us prevent KNOWN bugs. So it is totally acceptable that we sometimes miss a bug. But the approach we follow when we find that bug is very important. Suppose that QA team reports a bug in your published code. The first thing you need to do is to try to reproduce that bug using a test (preferably with an Integration/Acceptance test)
Then you edit your code to make that failing test pass. This way you have fixed that bug which is not the most important thing. By following this approach, you make sure that bug won’t happen in the future code edits anymore. The “Won’t happen again” is the most important intention of automatic testing.
SO… Remember! Never ever fix a reported bug without first creating a test to reproduce it.