This is a problem that I noticed in LibreOffice 4 but, as I'd seen LO5 (from
the LibreOffice site) did not have the problem, I assumed the bug had been
fixed. Unfortunately, now I've seen openSUSE's version of LO5, I see the bug is
specific to openSUSE.

What happens is that with data values which refer to a different spreadsheet,
the data values displayed in the spreadsheet are OK but some of them on a graph
are set as Y=0. Sometimes it's only one variable but it could be as many as 3
out of 5, say. 

The way I reset the values is to reset the data ranges on the graph; no data is
changed, just cycle through the actions.

I'm adding two attachments of graphs created from the same data but using the
two versions of LO5.