I would suggest just starting by filling out the bug report template, i.e. steps to reproduce, expected behavior, and observed behavior. If for some reason you can't provide a reasonable reproduction, the symptoms on their own can sometimes be enough for us to make an educated guess at what's going wrong.

Regarding whether you should post the root cause analysis: Per the current policy, the answer would have to be no.

I do personally have more nuanced thoughts on this, and I started typing them out... but then I realized that my reply was getting dangerously close to blog post length, so I decided to restrain myself and commit to turning it into an actual blog post later. In a nutshell, though, the problem is that even if there is such a thing as responsible use of LLMs for bug analysis, the only way we can currently be confident that someone possesses the required qualities for that is by working with them for a while.