This will be fixed. Actually, the problem is that sorting date in ascending order (earliest transaction on top) is currently unsupported. So if you use that sort order now, the balance calculation will be incorrect.
For now, the workaround is to restart Savings, and make sure you don't change the sort order in the date column. Better sorting will come soon, as well as the ability to make balance column stick. Will let you know when both are added.
Yi