I am seeing this same issue. It seems fairly random and I cannot reliably reproduce it, unfortunately.
May 10 2016
Running into the same issue. It works fine when I host the mission locally, but when I host it on a dedicated server the module doesn't hide the vehicle as expected.
This also affects the Seize module.
Just checked, as of 1.40 fn_returnGroupComposition still has Arma 2 classnames.