Folks, I've had several kits come back to me with issues to solve, and usually it ends up that they were soldered with what appears to be acid core solder. THAT'S A GIANT NO-NO FOR ELECTRONICS! You must use a noncorrosive flux, the standard is rosin core solder. I use the 63/37 Kester Rosin Core solder for my electronic work. Save the other stuff for plumbing!
I have a couple of the final sets that I've assembled and tested on the shelf if anyone is still looking for one of these.