1. When setting up a defense zone in the editor, tanks and men usually don't stay put in the zone they are supposed to defend. Some tanks even back completely off the visual map and just sit there!
THATS TRUE
But there is a trick how to force units to occupy the defence zone. Before/near(or inside) defence zone, u've to create a pre-defence contour, ie "pre_zone_01". And give order units to move to the "pre_zone_01", then command "take defence positions." In fact, units already have defence position and they just will define more precisely personal/local contours of the "defence zone". U may take as example mission "dust in the wind", where British soldiers takes defence positions.
They also sometimes advance when they are supposed to defend a zone.
That's a problem also. I may recommend to give command "ambush" after "defence" or even setup trigger "repeat ambush until victory/fail/event".
2. The Tiger VI occasionally doesn't respond to orders to move or go forward, placing it at a disadvantage while playing. I've been killed many times this happens.
I think u didn't check feature "always obey orders". Sometimes members crew scared and didn't want to obey order, ie driver doesn't want to go/loader to load shells/gunner to shoot.