"Add links" - error?

Hello, this is my first post, so please forgive me if this is a dumb question:
I have successfully installed Omeka S in a docker container as I first want to test it locally and then transfer it to the real web server.
I have an image of an article that is an object and contains an image that is also an object. I wanted to draw a rectangle around it and just link to the original image. However, using “Add links” just creates a spinning circle but nothing happens.
I tried to use the Dublin “reference” and “reference to” ressources but the circle does not change though the items are cross referenced. I think this might also be an installation problem. Any ideas or is there somebody who could describe how it is supposed to work?

Best regards
Holger

Think this an incompatibility due to mixing Omeka S v4.2.0 with 3.x modules from Daniel Berthereau:

Uncaught TypeError: can’t access property “literal”, vaTemplates is undefined
Uncaught ReferenceError: Sortable is not defined
Uncaught TypeError: can’t access property “literal”, vaTemplates is undefined