Plugin not working properly in aldryn_newsblog

[MarcMueltin]

I have installed the djangocms-unitegallery plugin via the Aldryn dashboard, then redeployed it on my test site.
When adding the unitegallery plugin in an aldryn_newsblog article, I am able to add pictures and fill in the title and description, but when I save it, then a javascript error occurrs for a few seconds and the added plugin is empty. Meaning: no picture is added, back to default. See screenshots.

When pulling the data locally on my machine, I can see that 'djangocms-unitegallery' has been added to my INSTALLED_ADDONS in settings.py, but not 'sorl.thumbnail'. Could that be the reason?
Not sure how to install the sorl.thumbnail addon as my local development environ threw me some error. But is it necessary or even relevant for that error?