Error adding user to license group

When adding a user to a license group, I'm getting the following error when clicking Finish in the popup window:

ATTENTION:

class [B cannot be cast to class java.lang.String ([B and java.lang.String are in module java.base of loader 'bootstrap')

Removing the below properties from the file IEConf/adapterservice.json doesn't help:

• local.xxx.binaryMode=objectGUID
• local.xxx.windchill.mapping.user.attributes=objectGUID