Some traffic does not reach our site

Hi! We have been experiencing some weird behaviour on our site that is hosted on our droplet (currently only one).

Currently we have a check on pingdom that checks the uptime of some of our services, this check has begun to regularly fail. The only error we see from pingdom is: “No data received from server”. This now happens almost every day. It’s not the services themselves that go down since we check the logs, but rather the API call that is suppose to tell us if they’re down is not responding.

Is there any built in protection on digital ocean that could block this traffic? The calls from pingdom is from a bot after all and is done regularly. We have tried to debug on our end on the server but can’t find anything that could block the calls.

Pingdom does it’s calls from random locations and which ones that fail seems random. One day a call from Atlanta fails and a call from San Francisco succeeds, and the next day vice-versa.

We’re hosting the same site in Sweden on another hosting provider with the same site (but different domain) with the same check but that does not fail.