In a datetime type chart, stacked columns have a weird behaviour, with one column columns seem ok (although a bit missplaced to the left):

But when adding more series to the stack, columns start getting thinner:

The hover effect in the column also seems missplaced:

Here's the pen from the screenshots: https://codepen.io/rudeayelo/full/OooKyR
Thanks for reporting, this should not happen.
I will take a look
Well that was fast 馃槃