That was a fun one to do a little surgery on. You are welcome. Looks just like my shop unit, nicely figured wood.
Side note: I always liked Black Walnut. Used to sit under a big Black Walnut at Grandpa's. We harvested loads of walnuts every year. If you've never husked walnuts, well, it's a mess, and shelling is a barrel of laughs too. But the rewards were great. And the wood from the crotch of that tree made some nice gunstocks after it was hit by lightning. Nearby was a Tulip Poplar I planted from 1st Grade Arbor Day, it's huge now. I like woods ! Started young...
Back to the thread: I think it was a bad solder joint (from back in the blind days) ... but getting a unit apart is usually destructive to the electronics and I tore these up, so we will never know for sure. Failed resistors are very rare, under normal use, so I think it was just a missed or bad solder joint that finally carbon-ed up.
I think (IMO) a sock or can-coozie is the best temperature bump device known. Been doing it since 2003. A little extra insulation may be just what is needed for some folks, or in cooler conditions, like winter.