lcfc80, I'm revisiting the topic of your thread because, in the course of dealing with the specifics in your post, I saw that in your first post in this thread you had described the procedures that might be causing your periodic drops, so I'm reopening this discussion.
Just to give you a partial answer on your original question for now, you describe erratic movements on your site as you gradually try to get it to move up in the rankings. I think your description might be pretty close to right on...
It's almost like a filter kicks in then lets go?
While Google likes changes that improve sites for users, it doesn't like certain kinds of frequent changes that might be trying to reverse-engineer its algorithm. When it feels that changes are being made for the sake of rankings, Google may
"change rankings in unexpected, counter-intuitive ways", trying to assess the behavior it's observing. There's a patent on this, one that I'm virtually certain Google uses frequently and in various circumstances. Here's a long and not always simple discussion on the patent...
Google's Rank Modifying Patent for Spam Detection https://www.webmasterworld.com/google/4486158.htm [webmasterworld.com]
Additionally, and related I feel to the core principles behind this patent, Google has instituted some fairly complex algorithms related to the use of its submission tools... also for the purpose of preventing manipulation. Regarding submission... not2easy was right on in her comment to you above. Frequent use of the Fetch tool may well get you in trouble...
If you are using the "Fetch as Google" tool to resubmit pages, they do not appreciate that. It is not going to help. If you add new content, submit a new sitemap.
Perhaps, I'm thinking, Google is applying special scrutiny to sites and submitters who've made frequent use of the tool, and identified networks they might belong to.
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Regarding your apparently simultaneous drop in rankings, I can't comment whether it was the only reason you dropped, but I was going to suggest that the sudden ranking of another site did sound like it might have been a hacked site. Since it appears that you're aware enough of that general mechanism to have guessed it yourself, you shouldn't be surprised that such a site popped up. The place to report that is Google, not here. I would also pay attention to how long the hacked and injected page stays in the position it's in.
It's hard for me to say, though, because of other issues involved with your site, precisely what might be causing the drop in your rankings, and whether the hack may be purposely targeting your search terms.
Note that Google's time to rank new content could easily be 6-9 months, but that apparently can be circumvented by churn and burn techniques. Perhaps the hackers were aware of this, and that's why the page was hanging around for a while before the page made this leap up. In any event, it sounds like your 'red widgets uk' niche is very competitive.