Recent clarification from John Muller of Google on Reddit reveals that Google cache system runs independently and does not affect the real time rankings of web pages in Google and the index.
According to John Muller, if your cache link in Google returns a 404 error, it doesn’t mean your rankings will get affected in Google. That means if you are anxious that your page might be de-indexed or there may be a drop in the rankings, nothing to be worried about that because that concept is now thing of the past.
The Google Cache 404ing is an internal issue with the Google Cache server and has nothing to do with indexing or ranking of the web page. It’s a different thing that earlier John Muller termed the web pages by default as inferior that haven’t cache link.