Why aren't my variant images changing on the front end?

[JamesB2000]

I'm having an issue where I have put images for each flavour on my variants but the image doesn't change on the front end. https://www.vaporshopdirect.com/products/lost-mary-bm600-disposable-vape-device

I checked on the console and it says there's an error in the theme-min.js, saying "TypeError: Failed to execute 'appendChild' on 'Node': parameter 1 is not of type 'Node'.". What does this mean and how do I fix this?