You're still making some assumption that the problem has something to do with that chip. I am an engineer.. I looked at your PDF, it doesn't necessarily look like that chip has anything you can flash. It looks like implementing it requires supporting hardware on the logic board. That DSP chip on your board could be 100% functional. If Fender doesn't document a way to do a firmware upgrade it's possible you can't actually flash the firmware at all. They could have used something that can't be re-written. If it's flashable you can make an assumption and try that if you can get the code. But you might need special tools/hardware/software to flash the chip. Those could cost more than a new amp. Heck they could cost 10x or 100x what the amp cost. And it'd all be a waste if the assumption the problem had to do with that chip was wrong.