I am also seeing about 40% loss when pinging that IP, so I would definitely not use those. Try the google DNS servers at 8.8.8.8 and 8.8.4.4 and if you keep getting health check failures I would suspect a problem with your line.
I was using the Google DNS for a while. Once every few months, Google would blacklist my IP, with a message that I had too many automated system calls into their system. They were right of course - the Peplink was pinging them too often. So I changed the test IP’s to ones I knew were just dumb routers in the net.
Thanks for the info rossh_pl, I have several Peplink routers that all use the Google DNS servers and I haven’t had any issues for the past few years - but this is good to know.