Orchestration rules not working for line level eff if is left blank

Summary:

Hi Team,

I want to check suggestions from the experts for the below issue which im currently facing,

I have created a orchestration process assignment rule as described below,

ordertype = Trade ( As per my requirement)

header level eff = True

line level eff is blank

The issue what we are facing that only when i select the line level eff and select blank as a value then only the orchestration is getting assigned(which require manual intervention ) and if i skip this line level attribute without touching the value then its not working. This behavior is impacting our importing process.