After some investigation, it looks like update 20.7.0+ is causing this error for us. We have not change a aip file at all, but when our pipeline started using AI 20.7.0+ the Product Code is no longer automatically re-generating. We've always updated the Product Version in the pipeline and that has been refreshing a new product code, but the newer version of AI seem to no longer behave this way.
I also saw this in the update notes:
But I can't seem to find any documentation on this new option, and am surprised the default implementation disrupted our existing project. Can you offer some advice on what we should do other than using an older version of AI?New option to control "ProductCode" regeneration when "ProductVersion" is changed