How to solve project steering problem statement 1?
We miss clarity on prioritization of epics taken into business analysis & design in a sprint, we do not know if the scope of sprint is sufficient to have all epics and user stories design ready when needed for a delivery team, we learned the scope of work was not always sufficient only ex-post, we miss the connection and coordination between epics taken into design and epics to be taken into delivery in the next sprint/s.
When you say "epic", which definition are you using? I'm familiar with two prevailing definitions. Some people use "epic" to mean a large User Story that has yet to be decomposed into work that can fit into one Sprint or less. Other people use "epic" to mean a container for other work, such as User Stories, bug fixes, or just arbitrary tasks that need to happen. Are you using one of these definitions or something else?
Is there a clear understanding of what the team needs in order to be able to decompose the work into Product Backlog Items that each can fit into a Sprint and then pull them into a Sprint at a Sprint Planning? Refinement is an ongoing activity to understand the scope of the work. In my experiences, with sufficient refinement, Sprint Planning becomes a very trivial exercise for a single team and only slightly more complex in a multi-team environment.
The Scrum Guide says:
Product Backlog items that can be "Done" by the Development Team within one Sprint are deemed "Ready" for selection in a Sprint Planning
Have team members discussed, and clarified between themselves, what it means for work to be "Ready"?