Hi,
Thank you for the accesses. I was able to do some debugging and found the problem.
It came from a double translation. The translation for the category's main description was done both while the category data was loaded in the popup, and when the translation mechanism run, while it should only be when the translation mechanism run.
So I've made a patch which fixes that problem.
The fix is actually quite simple. You just need to change the line:
$element = $class->get($category_id);
to:
$element = $class->get($category_id, false, false);
in the file administrator/components/com_hikashop/views/category/view.html.php
I've added the patch on our end too so to get the patch automatically, you can just update to HikaShop 4.7.1.