Trying to change the default value of a custom attribute in Project Object, with a default value defined.
When trying to clear the Default Value field, it gets populated again automatically with the previous value.
This problem is sometimes caused by an entry stored on the table odf_default_overrides table for that attribute.
Clarity PPM 15.x
If there is an entry on the table for that attribute, the solution would be to delete it having the services stopped.
1. Stop Clarity services
2. Connect to database and execute this delete statement:
delete from odf_default_overrides where object_code='project' and attribute_code='attribute_id';
3. Start Clarity services