Is the register sorted in date order? And not filtered? Try clicking the DATE column heading to sort by date and maybe reset the filters at the top.
If the balance is going down maybe it is a negative balance that is Decreasing. Maybe you have a credit balance instead of a positive balance. Like if you are overdrawn. Is the balance in Red or Black? Look back through your transactions and maybe you'll spot one that was entered backward. Or a payment in the charge column or a charge in the payment column. Look around back where this first started happening. Or maybe you are missing some charges?
I'm staying on Quicken 2013 Premier for Windows.