Well, two things:
Firstly, like when someone goes on the internet and asks: “What is the average amount of tar in a cigarette,” and a hundred people just ignore the question and immediately post: “STOP SMOKING” in all-caps, this is going to be a bummer, but: Are you absolutely certain, that you have to update this website, that was built in the era of Internet Explorer 10, and that it would not be much easier to migrate the data into a fresh install?
Secondly, if you are certain, that it is necessary: Have you tried deactivating all plugins, updating WordPress, then updating the plugins one by one, and then re-activating them one by one? In any case, please make a copy of the database.
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