Replying usefully when you know only part of the answer

State the part you can support, then mark the boundary of your knowledge. Give a safe check the author can perform and invite someone with direct experience to fill the gap.

Avoid presenting a guess as a fix, especially for security, data loss, or money-related issues. If your answer depends on a version or setting, say so. A careful partial reply can move the discussion forward without misleading others.

Which part have you personally verified?