Hello,
All these issues happen to my fresh new installation.
When I don’t use the single product page builder, some elements in the product page are not working properly. Most of the layouts are not displayed correctly, gallery is messed up in most layouts, tabs are not working (you click on them and nothing is happening – they just add the #anchor-link to the url) and related products slider is not working. All issues are fixed if I choose to build the product page with the builder.