We build our own jigsawed JRE for our application (see this question), but some (character) encodings are missing compared to run the application with a full JRE.
How to find our what module is missing to get all the encodings?
Most likely you are missing jdk.localedata module. As per docs:
Provides the locale data for locales other than US locale.
You can view all modules in your JDK by running java --list-modules and try additional modules if this is not enough.