show ltm profile http - interpreting outpu

That's a relatively high number of server errors (173 out of 194). Whilst I don't know the exact reason, my best guess would be a 5xx server response code perhaps? Have you tried running tcpdump on the serverside of the BIG-IP to see if you see 5xx HTTP status codes being returned? Alternatively you could assign an irule to capture the status code, something like this should work (but not tested):

when HTTP_RESPONSE { 
      log local0. "HTTP request: [HTTP::host][HTTP::uri] returned status code: [HTTP::status]"
}

Hope this helps,

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