Hover labels do not match x-axis value in scattermode "group"

We have come across an issue with scatter plots where the hover labels do not match the value of the x-axis on a (time) period axis. The problem only occurs when setting the _layout.scattermode_ property to "group" and shifting the markers using the _xperiodalignment_ property to "start" or "end".

Here is a codepen which demonstrates this behaviour:
https://codepen.io/apexi/pen/ExqXxKK