Unified hover box location problem

[nicolaskruchten]

In this pen https://codepen.io/nicolaskruchten/pen/qBrjNLJ?editors=0010 which is based on this morning's master build, when I hover over the July point, the unified hover box is nowhere near the right place:

More generally there is a problem with the unified hover box overlapping the spikeline when e.g. hovering on the March point, so appears to be a pervasive problem. Note that in this pen the hoverdistance is set to -1.

This is a v2 blocker.