nl/DS (alg 13, id 17153): No response was received until the UDP payload size was decreased, indicating that the server might be attempting to send a payload that exceeds the path maximum transmission unit (PMTU) size. See RFC 6891, Sec. 6.2.6. (192.33.4.12, UDP_-_EDNS0_4096_D_KN)
nl/DS (alg 13, id 17153): No response was received until the UDP payload size was decreased, indicating that the server might be attempting to send a payload that exceeds the path maximum transmission unit (PMTU) size. See RFC 6891, Sec. 6.2.6. (192.33.4.12, UDP_-_EDNS0_4096_D_KN)
nl/DS has warnings; select the "Denial of existence" DNSSEC option to see them.