I've seen the 3d gear issue mentioned many times in the past and I understand that's likely very easily corrected from "under the car" with three parts and minimal time. A detent ball and two springs accessible just forward of the CAGS. ZF DR mentions it in his FAQ.
Part ID'd as 627, 628 & 629 in his "shift system group" from this link
http://www.zfdoc.com/S640Parts.htm
Could it be a shifter issue? Maybe. Likely? I've no idea.
I'm starting a new thread looking for some ZF shifter help right now.