DEFECT: Story points show wrong totals when features expanded
Accepted answer
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FINALLY:
Especially with planning, my experience is that there is a lot you can do wrong in the process configuration and in using it, so it is very likely not a defect of the tool, but wrong expectation what should work and how.
For example PARENT/CHILD does NOT work across project areas. E.g. if a work item is in one project area and another is in another project area, roll up of story points won't work - but it will not tell you it does not.
Comments
And another point, since your description is not very good, there is actually a feature where the story points of stories are summarized and added up (across several levels) across parent child relationships for work items in the same project, displayed this way in plans and they are also added up and displayed at Epic level where Epic actually does not have story points as an attribute at all.
It is absolutely possible to add story points to the Epic work item type (which is wrong) and get confused because the ones manually given and the ones below show strange numbers/differences. Or you don't expect the roll up and see summed up values that are not what you expect, or, as mentioned, you expect roll up but it does not show because the relationship is across project areas.
The same issues can come up if you create a custom project area process.