GPT 5.5 seems to be degraded

After switching back to 5.4 a week ago because 5.5 was no longer reliable enough for my work, I tried 5.5 again today. The issues are sometimes difficult to describe, but I just had a simple and reproducible example: 5.5 generated a text in Markdown, and when I asked it to convert that text into another markup language, it returned the same Markdown text unchanged. I tested the same request with 5.4, and it correctly produced the text in the requested markup language. This is only one example, but it reflects the broader problem I keep running into. With simple tasks, the issues are already visible; as soon as the task becomes more complex, the output becomes increasingly unreliable and inconsistent.