After talking with a few drivers, train controllers, and signal techs, the biggest problem with electric staff working seemed to be the all to common theft of the copper wires that joined the instruments, and all the delays that went along with it.

In some sections of NSW (and possibly Australia), the copper wire was replaced with galvanized steel wire, and whilst galvanized steel has a higher resistance than copper, it is also much less desirable than copper, and, as a result tended to be left alone. By the time this conversion of ETS wires had started taking place, Train Orders had already started taking over, and the days of ETS Working became numbered very quickly.

I grew up in Gerringong on the NSW south coast and I personally remember every few weeks on the radio it would be announced "Signalling fault has stopped trains between Kiama and Bomaderry, Buses are replacing trains" which usually meant the ETS copper wire had been stolen (again).

I also remember on season 1 of Railroad Australia, there is a scene of Bernie Baker working his B61 out in country NSW and during a stop to change the staffs, in the staff hut, there is a big sign in the background that read something along the lines of "You are on camera and will be prosecuted for stealing safe working equipment".

I'm not sure how often staffs actually went missing, but I dare say the railways wouldn't have gone to the expense of putting cameras in a shed in the middle of nowhere because it wasnt a problem