Hello,
There are something you can try, because it seems that you use a custom version of hikashop frontend file css.
I suggest you to process a WinMerge to see differences between your current frontend file css and the last from the new HikaShop.
And especially around line 840 of the new Frontend file Css :
If you ever think you want to be able to fully use this new feature, I would recommend that you be careful to add all the css lines relating to this feature.
Hope this will help you to solve your issue.
Regards