Since a couple of days I get those errors again which I reported here about half a year ago: Nginx error: OCSP responder sent invalid "Content-Type" header
2018/01/19 21:15:58 [error] 5950#5950: OCSP responder sent invalid "Content-Type" header: "text/html" while requesting certificate status, responder: ocsp.int-x3.letsencrypt.org
2018/01/19 21:15:59 [error] 5950#5950: OCSP responder sent invalid "Content-Type" header: "text/html" while requesting certificate status, responder: ocsp.int-x3.letsencrypt.org
If you need further information just let me know.