Hi,
There is no "fix", it is a feature to implement.
The serials are stored in another table than the HikaShop order table. So, thanks to the trigger "onBeforeOrderExport" you can update the content of the export to add your own values (or modify the current values).
The idea is to load the serials for the orders, add a new column in the rows and populate the data with the serials.
"Fixing" it is the same thing than implementing the feature.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.