- Start from a clean Syncope (when creating a User the wizard should have the Plain Attributes step as latest one);
- Create a Plain Attribute and add it to an AnyTypeClass;
- Create a Type Extension for a Group to USER;
- Create a new user with plain attributes only, set a value for the specific membership attribute from the type extension and save user;
- Edit the same user and change value to the same attribute (add or remove all values if it's multivalue).
Result: changes on membership attribute are not saved.