Not able to run using custom plugins

I have a running Open Distro for Elasticsearch running on Docker, and it is running fine until I try to install some custom plugins. These plugins all work perfectly on Kibana v7.9.1 otherwise (not Open Distro version), and installing them works without issue.

However we cannot open up Kibana in the browser anymore. DevTools in the browser says that it was not able to load the script files for the plugins. Specifically the plugins each generate the following messages:

Loading failed for the <script> with source "https://......plugins.js"

then there is a second error, which I cannot exactly remember because the system is at the moment not available to me, but it is something like this:

TypeError: document.querySelector(...) is null.

I have googled for the first error, and people suggest that it might have to do with CORS blocking the scripts. Open Distro is running on a server and I access it through my local computer, but I have not been able to figure out if CORS is blocking the scripts or there is something else. The curious thing is that the plugins work in normal Kibana, but not with Open Distro.

Does anyone know this error and have a quick solution?