I (in the UK) just got a Yihua 959d this Xmas from Amazon sold by Yihua.
I already dislike opening new and "expensive" things, and I hate modding them (a confidence and warranty thing I guess) but I made a deal with myself to push myself a bit out of that comfort zone: if I was going to buy this then I must open it, check it out, and do any significant safety mods if needed.
In the main unit, there seems to be a minor PCB update to v4.1 (photo included below.) The only difference I can see is a cut-out in the board around the relay to presumably try to increase mains vs low voltage seperation? The soldering seems mostly quite neat, but I can see that the through-hole soldering, particularly on the component holding posts, hasn't flowed right the way through the vias (I'm not sure yet how badly this needs addressing?)
In the (S218A-labelled) wand, there seems to be a different board (or maybe it's just the underside of it.) Inside of wand in second photo below. I seem to have a lower-current fan (150mA vs 200mA.) Also, on mine, the separation between the wire of the reed switch and the bare metal cylinder/shield was even worse.

After probing the edge of the wire with a meter for continuity and discovering that bit really was lacking in any insultation where it was needed I decided to add some heatshrink (I don't know how well it'll cope with the temperature but I figured some attempt at improved insulation was better than none.) My dodgy mod in the final picture.
Otherwise, the wiring checked out: live and neutral not swapped at any point (thanks so much for the schematic @AndyBeez, it made it easy to check that the relay was defintely switching the live and not the neutral), good earthing continuity where it's was intended to be, OC between the primary and secondary, etc.
