A pretty good rule of thumb in plating (GSP may offer more, or better advice) is to keep the anode as close to pure as possible. Otherwise what may work at the outset is quickly disabled by the contamination absorbed in the electrolyte.
Some time ago I posted on my attempt to part karat gold with a sulfuric cell. Even after reading (Hoke) that it is not a good idea, my hard head determined that, for me, it was. I melted my karat gold, adding a substantial amount of copper, then cast anodes. I experienced exactly what I described, and to add insult to injury, during the night, the cell, which was made of ceramic, and hard fired, cracked, dumping a couple gallons of copper sulfate solution on the floor. Luckily, it was in my garage, where the damage was minimal, aside from my bruised ego.
If you study Hoke and try to absorb everything you read, discounting such nonsense as using gasoline to incinerate, you will slowly come to realize that everything is quite true----a realization that took me a few years.
Harold