I also get DC output on both channel. One about 0.37mV and the other about 0.14mV IIRC.(I'm glad that I'm not the only crazy one too measure channel balance right after measuring for DC and malfunctions right out of the box in any device I get)
Cleaning the flux isn't helping I guess they're using no-clean flux and it's reasonable that they don't clean it.
I first discover this when I connect them to oscilloscope and try to do the stereophile -90dB test...and I realized the offset from their measurement from other devices is much much smaller...