https://forum.sailfishos.org/t/connectivity-issues-related-to-ipv4-addresses-while-ipv6-works/8716
Next time you are in that situation, could you try whether it is to do with what I reported above? I know it is not an answer to your problem, but I would like to hear comments from other users if they happen to come across the same issue as I did e.g. Internet services with IPv4 do not reply but ones with IPv6 do?
Nevertheless the connectivity issue is a quite bad show stopper as a basic everyday smartphone feature and at least I am waiting for a a fix to be available soon or i’ll revert back to Android for good.