Hello,
It looks like a CSS issue since the "buttons" are out of the box.
I would recommend you to resize temporally your window in order to use the "responsive" features ; but reducing the size you'll have a "moment" where the box will be good and the button be available for "clicks".
In the plugin it would be difficult to add some specific CSS but maybe the HikaShop team will find something to add in the core to avoid such kind of issue with tables in the plugins' blocks.
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.