Although frustrating, it is very interesting indeed.
If I am looking at the right site, your ‘new page’ is not merely another page but a new major navigational menu item. My guess is that it’s a bigger ‘deal’ for google than we realize. I ain’t no xpert by any means, but it appears the algorithms are recalculating your whole site and then ‘settling down’ to nromal.
(it’s always easy to blame it on google algorithms) 