For people afraid of bricking their units, I can't stress enough how groundbreaking it is that they're acknowledging that risk and still offering to repair your unit. You pay of course, because this is a risk you took, but at least they will have a look at it:

    "Out-of-Warranty Repairs Available: In the unlikely event that something ever goes wrong with your hardware while using custom firmware, it is not covered under standard warranty. However, Polyend is always happy to help get your instrument back up and running through its official out-of-warranty repair service (standard service, parts, and shipping fees apply."

> groundbreaking it is that

Hmm, out-of-warranty repairs for music hardware is pretty standard, at least here in Europe. I've done this with Elektron, Novation, Korg, Adam Audio, Yamaha and a bunch of other brands before as well, with everything from speakers to synths. Is it different in the US perhaps?

I've even sent gear running custom firmware in for out-of-warranty repairs, without any questions asked about it. AFAIK, even if you're within warranty with custom firmware, they would need to prove it's specifically the fault of the custom firmware in order to deny warranty claims, they couldn't refuse it outright just because of the firmware on the device.