LDAP request failed timed out

I have ejabberd 15.07 running with LDAP authentication. This works fine for 95% of the times. Randomly a user is unable to authenticate. Looking at ejabberd.log the following log is displayed moments after it communicates with the server.

2015-10-21 14:20:47.227 [error] <0.7412.0>@eldap_pool:do_request:75 LDAP request failed: timed out 2015-10-21 14:20:47.227 [info] <0.7412.0>@ejabberd_c2s:wait_for_feature_request:756 ({socket_state,p1_tls,{tlssock,#Port<0.28105>,#Port<0.28107>},<0.7411.0>}) Accepted authentication for johndoe by ejabberd_auth_ldap from 31.112.96.168 2015-10-21 14:20:47.227 [debug] <0.7412.0>@ejabberd_c2s:send_text:1901 Send XML on stream = <<"<success xmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>">> 2015-10-21 14:20:47.227 [debug] <0.7412.0>@ejabberd_socket:send:187 Error in p1_tls:send: {error,einval}

If I try again it will happen the same, over and over, while other users can log in just fine and the chat keeps working correctly. Waiting for longer periods, let's say 10 ou 20 minutes, or restart the server, will allow the user to log in again.
Is there anything that I should change on my side to fix this issue?

Start with the ejabberd.log sequence showing the LDAP timeout, accepted authentication, and p1_tls send error, then inspect the LDAP authentication configuration and reproduce the intermittent failure. The payload names no source file or test; done means identifying the cause and documenting a verified configuration or code fix.