Troubleshoot something....

- Double Check issue, then confirm it, please do not put double effort.

- Try to show your clear logic, find solid evidence.

- Told the end user what you have done, what you gonna do and why.

- Set the right expectation for users if you cannot find root cause. This is very important under such scenario: Issue happened only once or randomly.

- Show best experience and guide users.

- Please do not make any conclusion which you are not sure.