You seem to have a very unreliable connection if the TCP retransmissions are anything to go by.

The payload of the POST request is not correctly encoded. The spaces in the field names or values should be encoded either as '+' or as "%20". Other special characters, e.g. % or +, also need to be encoded.

Wireshark shows that what looks like a normal request "teste=3" was sent and the bytes acknowledged. I see no response to that request from upstream, so I gather "unknown error" is internally generated. The other requests are taking about 2.5 seconds to fill which is not long enough to trigger any default time out I am aware of. How long after sending packet 29 does the client report the error? Where is the error being reported, and where (your error function, complete function...) is it being generated?