Created a Sprint but now I've no permission to manage it

Have created Sprint but now I have no permission to do manage sprints:

1. I've created one Board using only Project A (that I'm admin),
2. I've created one "Sprint 1" and put some issues inside,
3. Then... I've changed the filter to include Project B (that I'm not admin),
4. I put some more issues inside "Sprint 1", from Project B,
5. I want to manage Sprint (create more, complete, change dates) => No permission,
6. So, once again I change permissions to include only Project A,
7. I want to manage Sprint (create more, complete, change dates) => No permission.

Now I have created a Board and a "Sprint 1" and can't do anything, so:

1. I deleted the board,
2. I've create a new board,
3. The "Sprint 1" was already there, and again, I can't change it.

I'm managing the work of a specialized team across different projects that I'm not administrator. For me, the administration permission requirement doesn't make any sense.