Spreadsheet range name bug

Using Ubuntu 15.04, LibreOffice 4.4.6.3
A simple test case:

I create a data/range named DataSet1 (at A1:C1 through A3:C3)
I create another data/range named DataSet2 (at D1:F1 through D3:F3)
I fill in some data into each range.

Elsewhere in the spreadsheet I enter these formulas (in separate cells):

A20 has =sum(DataSet1)
D20 has =sum(DataSet2)

yet, when I look at the second one (D20), it has DataSet1 in it. No matter how many times I enter DataSet2, it changes it to DataSet1

On the other hand, if I use names like "DataSetOne" and "DataSetTwo" it works ok. Apparently, it's having problems with range names containing digits.
So, for now, I have a workaround, BUT I have many legacy spreadsheets that may be using names that get corrupted.