I'm in a very similar situation as the OP, though my failures have been total on the mid-bass with only HF produced by the speaker. I bought four of the DZR12's manufactured in late 2018 and purchased January of 2019. Within 6 months one of the units lost all midbass. I almost always ran the set of 4 together for moderate volume gigs as delays or splayed for coverage, mostly with subs and crossover filters from my X32 or Wing consoles in place. I cross them about 76Hz with the subs because that's an easily repeatable frequency on those boards.
Yamaha thankfully replaced the speaker under warranty after the local service center went to bat for me. The service center said they shipped a whole new speaker since the driver wasn't available and it had been several months in the shop. They sat in storage for most of 2020 until this summer when I finally had them out for a few gigs. Last weekend I discovered failure two, same symptoms and it's in the shop now.
I've run powered and passive speakers of my own and others' for years. These are the first failures I've had out of custom-built boxes, Mackie SRM450's, QSC's, JBL PRX12's and Yamaha DSR10/12's. I'm inclined to think it was a manufacturing issue from my own problems and the sequential serials noted in this thread. The boxes sound terrific when they work, but failures like these are perplexing to me.
