What is the most likely cause of the responses on lines 10 and 11 of the output below?

Silently dropping UDP packets with a high destination port would affect only that one hop; the fact that both hops 10 and 11 are unresponsive is more consistent with an ICMP response policy than port-specific packet dropping.

A completely downed device at hop 10 would prevent all packets from being forwarded beyond it, yet the traceroute output shows responses past those hops, meaning packets are routing through but ICMP replies are suppressed.

A local network connection loss during the scan would cause all remaining subsequent hops to be unresponsive simultaneously, not just the isolated hops 10 and 11 visible in the output.

Traceroute works by sending probes with incrementing TTL values and listening for ICMP 'Time Exceeded in Transit' responses from each intermediate hop. When hops 10 and 11 return no response, it means those devices are not generating or forwarding ICMP TTL exceeded messages back to the source - typically due to router configuration, access control lists, or firewall rules that suppress or rate-limit outbound ICMP responses.