I don't know this amp but most subwoofer amps are similar inexpensive class D amps (not critcizing, that is quite adequate for bass frequencies). I've replaced amps in subwoofers the blew. I think the one I ordered from HSU was about $250 and took 10 minutes to install.
I'm guessing something in the channel is overheating. could be a defective thermal overload ($2 part). when you get the amp out you may see obvious signs of overheating. if not, ask ML how much it costs for them to just send you a replacement amp. You may be surprised.
If it was mine, I would troublshoot it myself and likely fix it for $10 or less but to pay someone to do the troubleshooting will likely cost more than the price of a new amp. Yes, that is the service industry world we live in. I recommend every young person study physics and become self sufficient. I've yet to have one take my advice.
Jerry