Is it reasonable for a development team (or person) to expect complete UI/UX when you’re the sole UX person on a team?

I work for a small startup, and I'm the sole UX designer, responsible for a couple of products. I also have the duty of ‘product owner’ managing the sprints and epics we tackle every two weeks. I’ve implemented a UX design process, that has been in place since the start that the stakeholders and team understand clearly. There is full transparency into this process, the documentation, the UI and the prototypes. For example if we have an idea, or we have an hypothesis. I research the idea. I make sure it aligns with our target audience (via persona’s). I build out scenarios and user flows. The I go to wireframes and/or prototyped and/or design - depending on the scope. For larger epics we do user testing.

The issue I’m having is with the expectation from a developer that the designs be 100% complete and accurate. I feel this is not reasonable given the size of the company we are, and the breadth of duties I (and all of us) have. I’ve worked with companies in the past, where if there were a gap in the design or UX, it’s brought up with myself or my team, and we provide the solution then and there. Problem solved, we all continue moving forward.

This is becoming frustrating - as it’s beginning to erode the teams moral a bit. For instance, when there is a QA bug or gap, which I identify, the usually response is “…it should have been in the design then”.

Looking for ideas and advice on how to mitigate this. Thanks in advance.