This unit doesn't have thermal protection but it has a DC offset
protection. This model was extremely reliable but I repaired one that
had both amplifiers completely wiped out. Even though I told the
customer I wouldn't void his warranty if he told me how he managed to
accomplish this feat, he wouldn't divulge what he did.

Plugged the speaker outputs into an AC wall socket?

I had an amplifier with DC offset protection, in which the amplifier failed,
and the protection failed, at the same time, an incredibly unlikely
coincidence. The DC damaged one of my speakers.