had a little issue with the script - i selected the group and hid it, but in reality only the vehicles (with troops inside) were hidden. so when i used {_x enableSimulationGlobal TRUE; _x hideObjectGlobal FALSE} forEach units group1 it didn't work. however, changing _x to (vehicle _x) fixed it. the final script that worked for me looks like this:
{(vehicle _x) enableSimulationGlobal TRUE; (vehicle _x) hideObjectGlobal FALSE} forEach units group1;