That is not a bug, it is by design.
What is happening is you are posting a very short answer with a link and the system is picking that up automatically as a low quality / link only answer.
When you post a link answer you MUST include the relevant content from the link in the answer and leave the link as a reference, we already have a review queue for this.
To be fair to you, I had no idea this even a thing and it seems like it could be a poor way of handling these kinds of answers in some situations.
You are welcome to take it here and request a change but I doubt it be well revived.
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