Problem with formula.... =sum(number1,[number2, ...)

When I click on a cell to drag down to include other cells, it is doubling the current cell I am in and continues to double the cell when I try to move to any cells. I have not had any issues until now. I have to completely delete the formula and start over but I can only get it to work if I click on each box individually. I am not doing anything different then before, did something change?

This is what I get and the cells do not change....=SUM([Used Qty.]1676:[Used Qty.]16801676:[Used Qty.]16791676:[Used Qty.]16781676:[Used Qty.]16771676