Well I have been perfectly happy with my z1, everything was working fine until I tried to install the backup camera. I have read all the threads on this subject and mine seems to be a bad backup input into the Z1. Everything is grounded right and the backup camera works fine if you plug it into the video input but is terrible plugged into the backup input.
I bought it on ebay so I called the seller which is a large on-line dealer with great ratings. The unit has been installed for about a month or so. The store apologized for the problems I was having and said they would replace the unit with a new unit. I was given an RMA number and I am now waiting for the new unit to return.
My unit was working perfect other than the backup input, I hope the next one does as well. I will also lose all my saved stuff on the unit but I really want it to work properly in every aspect.
I said all this to say it really sucks to have to pull the unit and do without, I now sympathize with others that have done the same!!!