The article says that part of the need to get programmers back in the project is to be able to get exact readings on the amount of energy that's being used and

The article says that part of the need to get programmers back in the project is to be able to get exact readings on the amount of energy that's being used and the amount left. It appears like they are currently working with estimates (e.g. they cite a use of 3.2 Watts but it's actually 3.0 due to margins of error in the original design. Now they want to know exactly how much power is consumed). So maybe they don't need fixes in the traditional sense that something is broken, but fixes in that they need the spacecraft to do stuff that wasn't designed for. Another example they cite is when they revamped the software in 1990 so they could better automate certain functions since they were preparing for the interstellar part of the journey and they needed certain automatic procedures which apparently were done manually in the past.