There is no Sandbox and it is a waste of time to think of what is happening that way. Your temporary boost from the Freshness Factor wore off and you now rank where you deserve to rank.
I agree with the first half of your post but disagree with your labeling of this as “The Google Dance”, that just not accurate.
The “Google Dance” is a term that was originally coined to describe the shift in SERP rankings after a major algorithm update. Over time Google realized that major updates tended to be a little too disruptive and they switched to a more incremental upgrade process. Now, anytime Google does a minor update, tests a new algorithm tweak, or does a data refresh, ranking fluctuations are called the “Google Dance”. The bottom line is that the term implies that Google has changed something on their side that has caused a shift in SERP rankings.
In this case, the OP’s shift in rankings has nothing to do with changes from Google’s system but is a standard feature of their algorithm. It is called the “Freshness Factor”, or internally at Google as QDF (Query Deserves Freshness).