Hello,
In order to allow us, to better understand your root issue can you process this different checks please :
1. From Main HikaShop configuration => Display tab, then Default parameters for products part.
2. Set the Popup mode option to your required value, then Save.
=> See if that solve your notice issue or not.
3. Go to your relative Item Menu configuration, and Products options tab.
4. In Product data display part, find an as previously define your required value, and Save
=> See if that solve the error
We awaiting your detailed results, this will help us to solve this issue for our futures release.
Regards