We’ve improved how errors are grouped for Ruby, PHP, Python, and Node.js projects to minimize duplicate errors being reported upon code modifications and to provide complete visibility into the impact of all errors over time.
New error groupings will no longer be created due to the line numbers changing because the improved grouping algorithm is based on the section of code an error is originating from rather than the line number, which can change when code is modified.
To upgrade, go to Project Settings > Default grouping.