A number of people have raised the following through support, so I thought it was worth documenting in the forum.
When using the Weekly Historical-Forecast content and importing directly from accounting packages, there is a disconnect between the historical income statement data and historical balance sheet data, due to the way accounting packages provide the balance sheet data.
Using a simple example of $100 income for four weeks, when running the import assumptions tool at the end of the month, the following pattern of data is brought in: