I am aware of this question, but, frankly, other than emphasizing and re-emphasizing that "Sprints belong to boards not projects" and "Issues do not belong to boards", the given answers provide little practical advice as to how the problem can be fixed. (Also, I'm not 100% that my issue is really the same.)
So, here goes my problem: we originally only had one project, SP, but then later added two more projects, FE and HF. Each project is supposed to be on it's own sprint cycle. On the "Projects" page I see all three projects, each with their own board. When we originally split out the new projects from the original SP project, everything went well for the HF project, but the FE project and the SP project are still somehow linked. Specifically, it appears that both projects share the same sprint objects. This manifests itself in the fact that starting an SP sprint will also start the FE sprint (and vice versa). Also, when I change the name of the FE sprint, it will also change the name of the SP sprint, and vice versa. So, for all intents and purposes, it appears that the FE sprint and the SP sprint are really one and the same object (though they do show the correct issues in their respective boards). This linkage appears to be retained for all future sprints as well. As I stated earlier, each project has its own board, so I'm not sure what else to check.
How can I separate the SP and FE sprints from each other?