If you can't prove the edge case to be impossible, you must assume it to be possible. If it is possible, then it is inevitable that it will eventually occur, and sooner rather than later. If the edge case hasn't occurred in testing, that may be a hint that test coverage is incomplete.

1. Accept the feedback.
2. Before making any changes to your code, try your best to build a test for the edge case and see if you can get a test failure (proof that the issue exists). If it's impossible to create a such a test case and get a test failure, then you may be able to conclude that the edge case is actually impossible (although I'd be hesitant to draw such a conclusion).
3. If you can get a test failure, apply the appropriate code change to pass the test.

For the good of the product, you probably want to be able to produce the edge case and induce a failure, so that you can apply the fix and have confidence that a potential problem has been avoided.

If you can't prove the edge case to be impossible, you must assume it to be possible. If it is possible, then it is inevitable that it will eventually occur, and sooner rather than later. If the edge case hasn't occurred in testing, that may be a hint that test coverage is incomplete.

1. Accept the feedback.
2. Before making any changes to your code, try your best to build a test for the edge case and see if you can get a test failure (proof that the issue exists). If it's impossible to create a such a test case and get a test failure, then you may be able to conclude that the edge case is actually impossible (although I'd be hesitant to draw such a conclusion).
3. If you can get a test failure, apply the appropriate code change to pass the test.

For the good of the product, you probably want to be able to produce the edge case and induce a failure, so that you can apply the fix and have confidence that a potential problem has been averted.

The whole point of code reviews is to put additional eyes on the code. None of us is immune from mistakes or oversights. It's all too common to look at a piece of code many times and not notice an obvious error, where a fresh pair of eyes can pick it up immediately.

As you said, you've implemented a new algorithm. It would be unwise to draw conclusions about the behavior of your new algorithm based upon the behavior of or observations about its predecessor.