The Product Owner, Tech Lead, and Developers should be consciously working together to reach a goal. Identifying something as a defect should not be pejorative. It should be a means of improving process and ensuring cost effective delivery of features. It is not personal. It is a way to see that there is a flaw in the system that needs to be investigated.
From the vantage point of the Product Owner, identifying a defect is important to ensure both system correctness and to manage cost. If a development team cannot consistently deliver on the specified requirements, or if that consistency is derived of trial and error approaches, a product or feature may become impracticable for the needs of the business. A product owner should ask, did I specify this completely? What additional verifications could I have specified to have avoided this.