@Greyzy
Hello!
Our regional (country / continent / world) domain names for "best" servers change their records frequently, according to https://airvpn.org/faq/servers_ip/ . That's why you can get a different resolution every 5 minutes. This matter is totally irrelevant for the problem you experience, don't worry about it.
It is possible that Vodafone is messing up your DNS queries. We saw this shameful behavior in the past, many years ago, by Vodafone Italia, which re-directed anything to port 53 to force resolution of names by its own DNS servers and also prevent any other protocol to port 53. We can't rule out, according to all the data you provided, that this is the case for you too, with the addition of some acrimony against our VPN domain names.
The problem should get resolved by DNS over TLS to port 853. Unfortunately Windows 7, as far as we know, can't support it, but Windows 10 (which runs in another machine of yours) and the router can: please test it. Once the router is configured properly for DNS over TLS, you can configure your Windows 7 system to query only the router for names resolution (in the DNS settings enter only the router address in your local network).
Important side note: please consider to drop Windows 7 as it is an abandoned system ever since a long time ago.
Kind regards