Hi @rvogelgsang,
Sorry to hear you are having trouble! If you had a bit more details that might be helpful.
For instance:
What environment you are running FusionAuth in and what client package you are using? Sounds like maybe our typescript client?
Where are you setting the custom ID and what errors are you seeing?
An example code snippet if possible
Additional context about what you are trying to achieve in your code
etc
If this is ultimately a bug, we can file a bug report as well. Thanks and let us know!
Thanks,
Josh