SSL Broken pipe PHP warning

A few PHP warnings we found in error.log file which relates to Defender. Can you please let me know what it is? (Note i replace the actual directory name to "xxxxx")

[Mon Mar 06 12:42:54.490995 2017] [:error] [pid 23754] [client 144.76.105.53:45110] PHP Warning: fwrite(): SSL: Broken pipe in /var/www/xxxxx/wp-content/plugins/wp-defender/app/module/audit-log-module/component/class-wd-audit-api.php on line 127
[Mon Mar 06 12:42:55.719517 2017] [:error] [pid 23754] [client 144.76.105.53:45110] PHP Warning: fwrite(): SSL operation failed with code 1. OpenSSL Error messages:\nerror:1409F07F:SSL routines:SSL3_WRITE_PENDING:bad write retry in /var/www/xxxxx/wp-content/plugins/wp-defender/app/module/audit-log-module/component/class-wd-audit-api.php on line 128
[Mon Mar 06 12:42:55.719637 2017] [:error] [pid 23754] [client 144.76.105.53:45110] PHP Warning: fwrite(): SSL operation failed with code 1. OpenSSL Error messages:\nerror:1409F07F:SSL routines:SSL3_WRITE_PENDING:bad write retry in /var/www/xxxxx/wp-content/plugins/wp-defender/app/module/audit-log-module/component/class-wd-audit-api.php on line 129
[Mon Mar 06 12:42:55.719685 2017] [:error] [pid 23754] [client 144.76.105.53:45110] PHP Warning: fwrite(): SSL operation failed with code 1. OpenSSL Error messages:\nerror:1409F07F:SSL routines:SSL3_WRITE_PENDING:bad write retry in /var/www/xxxxx/wp-content/plugins/wp-defender/app/module/audit-log-module/component/class-wd-audit-api.php on line 130
[Mon Mar 06 12:42:59.741399 2017] [:error] [pid 23598] [client 202.80.214.248:62116] PHP Warning: fwrite(): SSL: Broken pipe in /var/www/xxxxx/wp-content/plugins/wp-defender/app/module/audit-log-module/component/class-wd-audit-api.php on line 127
[Mon Mar 06 12:43:00.300398 2017] [:error] [pid 23598] [client 202.80.214.248:62116] PHP Warning: fwrite(): SSL operation failed with code 1. OpenSSL Error messages:\nerror:1409F07F:SSL routines:SSL3_WRITE_PENDING:bad write retry in /var/www/xxxxx/wp-content/plugins/wp-defender/app/module/audit-log-module/component/class-wd-audit-api.php on line 128
[Mon Mar 06 12:43:00.300518 2017] [:error] [pid 23598] [client 202.80.214.248:62116] PHP Warning: fwrite(): SSL operation failed with code 1. OpenSSL Error messages:\nerror:1409F07F:SSL routines:SSL3_WRITE_PENDING:bad write retry in /var/www/xxxxx/wp-content/plugins/wp-defender/app/module/audit-log-module/component/class-wd-audit-api.php on line 129
[Mon Mar 06 12:43:00.300566 2017] [:error] [pid 23598] [client 202.80.214.248:62116] PHP Warning: fwrite(): SSL operation failed with code 1. OpenSSL Error messages:\nerror:1409F07F:SSL routines:SSL3_WRITE_PENDING:bad write retry in /var/www/xxxxx/wp-content/plugins/wp-defender/app/module/audit-log-module/component/class-wd-audit-api.php on line 130