Maxima install

I have been installing stereos for a few years now and I have a problem that I cant reason. I deal with Panasonic head units. Every time I install a Panasonic in a Maxima I lose my ground for the hu and have to run another behind where the hu sits. I thought it might be something to do with the Nissan wiring that it didn't have a ground to begin with, but I replaced an aftermarket hu already in a Maxima  the other day that was working fine, but when I went to install the Panasonic I didnt have a ground. Obviously the aftermarket hu before had a ground bc it was working fine. I did not see anything special done on the previous install. It was just your regular plug and play. When I spliced the Panasonic in to the adapter harness the hu lost ground just like all the others I had done.