Hoping somebody may be able to shed light on the below.
We manufacture and sell a Top #50 product within its major category (e.g. Beauty, Electronics, Home & Kitchen). The product itself has been positioned #1 in organic search for all major keywords for the past 6 months. We also had a very good Black Friday week which further increased the ranking and sales against our competitors.
On Sunday 30th November, all of our rankings for EVERY single keyword dropped off the face of the earth. Our #1 positions all dropped to 13 and below, and one of our keywords dropped from 2nd to 150th. We have made no changes to the product title, keywords or description recently. This has hit our sales hard.
What we did however was follow some new keyword advice and removed repetitive keywords that featured in the title and added new long-tail keywords instead (for example, the product name and most searched for strings are no longer in the keywords). This was done on the 13th November which is 2 weeks before this drop in rank. Is it possible that this could have caused the issue (with a 2 week delay) and if so, it means all Keyword advice about non-repetition is not true.