I’ve never heard of anything but the send away service or a local electronics repair. It’s probably capacitors, I guess you could just replace them all?
But, you can certainly replace the amp unit with an aftermarket dsp and separate amplification. There is coax digital and rca left right available, so it isn’t too hard to do, mostly a packaging (size under the seat) issue.
This is around $800, depending on the amp and dsp you choose.
There are 12 channels of separate amplification, but several of them are low wattage (2nd row door speakers, tailgate speakers).
You can read through that section of my build thread for more detail.