This is an further report of issue #627
Codepen
Version using Apexchartsjs 3.6.12: https://codepen.io/ChrisMaunder/pen/BgOYwq
Version using Apexchartsjs 3.8.0: https://codepen.io/ChrisMaunder/pen/EBeQvK
Explanation
This seems to be the same issue as #627 except this affects "area" and "line" type charts.