I kent ye widna let me doonThe second version of the machines (White ones) which remained in use up till 2009 proved to be very unreliable towards the end, with passengers often having to be let on for free. The reason for it being scrapped in 2016 was due to a decline in use and the rise of "smart ticketing". A good concept that did work, but became outdated by better technologies.
On all the buses native to the fleet up to the SV08 B9TLs you can still see where the machines used to be as the hole on the cab wall has just been panelled over. (see link below).
https://www.flickr.com/photos/jordanadam44/36729695583/
As a wee aside, a book I bought a couple of years ago showed a photograph of a Northern Olympian, part of the then "Grampian Scottish" fleet, doing a run to Buckie on the 305. The caption stated that due to the fact that the bus had "autofare equipment" installed, it had to have a conductor for routes outwith the city (Aberdeen). I started going to secondary school in 1986, around the time when Northern were introducing dual-door Olympians for the Aberdeen City fleet, and a few of the older 'deckers were sent north for repainting, with a few remaining permanently. They retained their fareboxes for a good while (bagged over and tied), but had regular Wayfarer I machines installed which didn't quite fit in the original mounts.