Flange Back Adjustment Sony Z1u - Service Manual?

I am trying to use my old Sony Z1u as a B camera but have encountered an apparent back focus issue (i.e. when I zoom in, focus, and zoom out, the image goes soft). Has anyone here seen that problem, and more importantly, does anyone here know how to fix it?

When I encountered that same problem on my EX1R I discovered that the camera's hidden menu offers an automatic "flange back adjustment" procedure.

Despite extensive searching, I haven't found a comparable fix for the Z1. But I have found a website that offers, for $15, a download of the Z1 Service Manual. Before I plunk down the cash for what might be a useless purchase, I thought I'd ask here: does anyone know of a procedure for adjusting back focus on the Z1? -and, does the service manual have the fix?

The closest I've come to an answer is either (a) send the camera to Sony, which will fix the problem for a rather large fee; or (b) buy the RM-95 remote, which enables you to access some hidden menu.

Thanks very much - perhaps hundreds of dollars of very much.

Bob C