4. Product Owner or Project Lead focusses either heavily on design or on technical aspects
Even if decisions are taken, the Product Owner (Decision Maker or Project Lead) should neither focus in the beginning on UX & Design requirements only, nor on the technical aspects of the project.
Why is that?
This is pretty easy: a successful implemented and delivered project relies on the holistic planning and overview. Project Managers are completely wrong, if they think we need to finalize every UX & Design concept before we could start with the functional implementation. This will result in disappointed team-members, when they realize that the shiny designs can`t be realized sometimes, cause there are natural technical constraints.
The other way round is also wrong: don`t think of doing first all technical aspects for example, and then start with the UX & Design. And also here, if this happens, the technical circumstances could drive the UX & Design concept, what you should also avoid. The customer should be in the center, no one else. A balanced planning of the important topics is key, together with a cross-functional development approach, where the user stories (agile expression for requirements) are treated holistically, with technical & UX stakes.