Pictures disappearing when no default variation is set

Hi, as the title says: my featured images disappear when no default variation is set (it does display when a default is set, but I do not wish to set one). I’ve tried disabling all my plugins (except woocommerce + this plugin) but no luck.

Website example is here (wip) – http://pivotdesign.co.nz/pioneer-nursery/buy-plants-online/shelter/acacia-floribunda-sallow-wattle/

Can anyone help me here? Thanks

https://wordpress.org/plugins/woocommerce-radio-buttons/