My WF-139 terminates on my RCR123s at ~4.20V, but since it doesn't use CC followed by CV correctly, the cells drop to 4.16 within moments of the light going green. Then if you leave the cells on the charger "green" for about 8 hours, they will come back up to ~4.20V. With 17500 and 17670 cells the behavior seems to be different, It seems to CC charge up to around 4.23-4.26V give or take, at which point it goes green and the cell falls to ~4.20V (sometimes over sometimes under), then continues trickle charging them, after 8 hours I've seen it push 17670 and 17500 cells as high as 4.29V.
My gut on these things tells me that 90% or more of the WF-139 chargers shipped are probably *junk* with improper termination and overcharge problems. My gut also tells me that ~25-50% of owners will not "catch" the charger being bad necessarily, or it may behave differently with their cells and never appear to have a problem. There's a lot more to the equation of how problematic products get reported. Of course, as soon as a problem starts cropping up, and a lot of people start reporting it, owners who have not had the problem may come out to defend the purchase, beating back the problem. It's like the stock market, A bunch of people sell off, and it's almost always rebounded by a bunch of people sweeping in to buy at the newly reduced price.