Hi,
In Joomla, you can assign a module to a position and to some Joomla menus (also called itemid).
In HikaShop, we also provide a setting to configure modules which would be display under the product page.
Now ; the modules you configured in Joomla are managed entirely by Joomla and HikaShop have nothing to do with that.
If you open a page using a specific itemid ; the module configured to be display in that menu will be displayed by Joomla (aka : not by HikaShop).
In order to have nice URL ; you're using the same ItemId for the product listing menu and for the product page.
But, by doing that, you're display the product page with the same menu than the product listing.
So ; there is no bug and the problem is not HikaShop.
The problem isn't Joomla either ; it is a current limitation in the Joomla module/menu system and some extensions, like "advanced module manager" allow Joomla to improve that.
I hope that I'm clear enough.
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.