Since midnight (AZ, USA time), I’m getting those errors in the nginx server error log.
It’s the first time I’m getting those errors since Let’s Encrypt has been installed.
2016/12/12 00:21:19 [error] 10619#10619: OCSP_check_validity() failed (SSL: error:2707307D:OCSP routines:OCSP_check_validity:status expired) while requesting certificate status, responder: ocsp.int-x3.letsencrypt.org