Just one question: did you try swapping out the ESPs one with the other to make sure that it really is the ESP module?
Any yes, this last batch has been a real problem. They work fine when I program them, but some (MUCH more than usual) give up. In fact I have started sending out spares with each order, because the modules cost $1, but the postage costs me $7.
Just want to add... your "bad luck" with ESPs is bugging me, it should not be happening, and I wish we could come up with a definite cause. I have 38 ESPs operating in my house at last count, 10 in clocks, 27 in a home brewed energy management scheme and one reporting outdoor humidity and temp. They really do work quite well. I've had maybe 4 or 5 DOA from the vendor but have only had 1 that worked for a while and then mysteriously quit.
And... I see Ian has just posted and confirmed the bad batch theory...
Look into it later when the dust is clearing off the crater.