I have run half off all the NTP servers in Costa Rica for many years now. These servers serve hundreds of devices on the internal ISP network they are part of and thousands more outside. Almost 2 months ago the responses they give don't get logged or don't reach the Los Angeles monitoring Station. This only happens using IPv4, on IPv6 it works fine.
Today I decided to take all the servers off the NTP pool since apparently there is no way to fix this. Ask suggested to "see if someone else can monitor the server for a few days"
So here are 2 of them: 18.104.22.168 and 22.214.171.124
So, if anyone can monitor these servers for the next couple of days it would be very much appreciated.