Cloudflare could not understand our reply.
WHAT IT MEANS
Our server returned something Cloudflare could not interpret, or the connection dropped mid-response.
THE COMMON CAUSES
A PHP fatal error producing a malformed response The response exceeding a size limit Headers that are too large, frequently from excessive cookies A crashed process Resource exhaustion
WHAT TO CHECK
cPanel > Metrics > Errors at the time of the error cPanel > Resource Usage for a spike
If our log shows a PHP fatal error at that moment, that is the cause and Cloudflare is merely reporting it.
IF IT IS INTERMITTENT
Usually resource pressure. Check usage graphs against the times.
IF IT IS CONSTANT ON ONE PAGE
That page is failing. Enable debug logging and reproduce.
WHAT TO SEND US
The time, the URL, and whether it is constant or intermittent.
Mention that Cloudflare is in use, and give the error number.
THE DIAGNOSTIC SHORTCUT
Pause Cloudflare and load the page directly. The underlying error is usually then visible.
