DNS issue

Good day :) we are experiencing some issues with one of our websites, hosted on our dedicated server. Most of the time, the website seems to be "up and running" correctly, however we receive at least 10 emails a week visitors cannot reach the website. This is strange because all the other websites that are hosted on the same server do not experience similar problems. Sometimes these messages say the server cannot be reached, sometimes an error appears saying: "The server at [website.com] can't be found, because the DNS lookup failed. DNS is the network service that translates a website's name to its Internet address. This error is most often caused by having no connection to the Internet or a misconfigured network. It can also be caused by an unresponsive DNS server or a firewall preventingGoogle Chrome from accessing the network. When we run some online DNS check tools, often they display some errors/problems, like: None of the name servers responded in a timely manner Local NS list does not match Parent NS list Serial numbers do not match No SPF records found Even when these errors show up, myself I can reach the website without any problem. Soo we contacted our hosting provider, to see if they could find the problem. Basically, this is what they found: " You have the nameservers on that domain set to ns1.ip.example.com and ns2.ip.example.com. I believe the nameservers should be ns1.example.com and ns2.example.com I don't know where the ip.example.com is set up and I believe that is what is breaking your site. " Before changing anything I decided to post this here as I don't want to edit anything on the server that might affect other websites on this server. I am not sure why the nameservers on this server are set to ns1.ip.example.com. Can I simply change this to ns1.example.com without running any risks? Should I change this on a server-level (if possible) or in the DNS Zone file settings of every page individually? Many thanks for your time :)