Inconsistent Behavior: First Post Fails with Timeout, Second Attempt Succeeds

When I tried to post a comment in ArcBlock Community, the first attempt failed with the errors “timeout of 20000ms exceeded” and “Request timeout: please retry the request later.”

But when I tried again without changing anything, the comment was posted successfully.

It feels confusing because at first it looked like a complete failure, but then it suddenly worked on the next attempt. What is actually happening here?