Thank you for your query at DoctorSpring.com
I understand your concern.
Both Endoscopy and barrium studies are accurate in detecting paraesophageal hernia if properly done.
Might be while doing barrium study specific maneuver might not have been done to delineate the hernia.Also in endoscopy personal variations will be there.
Other possibility would be Achalasia cardia with diverticulum (by considering your monometry and other investigation reports)
Please provide your symptoms and the report of your barrium study finding.