No Preview, if Following Current Instal Instructions

[luxlogica]

The current installation instructions are:

To quickly get an example including the previews of the builder working, 
copy the files inside the sandbox folder into the respective folders and 
add the following field declaration to a blueprint:

However, doing this in both starterkit and plainkit produces a builder field with 'preview' buttons that when clicked do nothing. It all seems to work as intended, except that we have no preview.

Using K3-b6, with the latest Kirby folder nightly.