Export hides lines when using zones

[enersis-pst]

Expected behaviour

Chart will still be the same after exporting the chart

Actual behaviour

inside chart the lines which have zones will be hidden after exporting it

Live demo with steps to reproduce

https://jsfiddle.net/nxbgdhvj/3/
use the export button and export as any type (for example png)
the lines are than not shown

Product version

latest

Affected browser(s)

chrome

[enersis-pst]

looks like zone objects will be cleaned
before

after

[enersis-pst]

someone describe the same problem here https://www.highcharts.com/forum/viewtopic.php?f=9&t=47401

[jszuminski]

Works well with 11.2.0: https://jsfiddle.net/BlackLabel/3fyjL2eh/
Seems to have been broken with 11.3.0: https://jsfiddle.net/BlackLabel/gjpom8cz/

[jszuminski]

Fixed with: #20558
Here's a demo from master: https://jsfiddle.net/cuetrbfw/