As you can see you don't get any response back from NTP server (which listen on port UDP 123). Routing table seems fine. Are you using some firewall? Does any other network action works like curl?
As a temporary workaround you could set time like this (from autostart.sh maybe periodically):
Hello, I am currently having the same issue on a RPi1 with LE 9.1.502 and can confirm the above workaround work. I haven't yet been able to determine what is causing my NTP packets to drop. Any help on this issue would be appreciated.