I've entered the transactions and the credit memos a few different ways. I entered all the invoices first, then the credit memos, but I also did it a way were I entered it in the exact order you mentioned, recording transactions on different dates. In both cases, I was able to successfully go through the process as I outlined.

I hear what you're saying and can appreciate the skepticism with there being data damage to the file. Data damage can sound like a large, overarching thing, especially when throwing the word corrupt in there. Yet, often times, it causes little things, such as this, and only affects that specific thing or area. Something may have happened when upgrading the file from the 2010 to the 2020 edition of QuickBooks Desktop that affected those transactions. If the agent didn't go through this with you, feel free to check out and try the steps in the Fix data damage on your QuickBooks Desktop company file article.

I hope that helps clear it up.