I used to get a few..
610s, 612s etc in for repair. They were straightforward enough to work on, though I never really took to them, partly because a few of the examples I came across had already been hammered and suffered from the worn out inner chassis syndrone. In particular, the black inner chassis used to wear badly around the rear wheels, which would then go skew wift and fall out. Later chassis were improved upon but they now seem to be an obsolete part.
The other thing that used to sometimes wear out was the little white plastic fork adjusting the front rollers, though, to be fair, these would generally give good service. A worn one would cause the handle to lean inwards.
Early 612s had metal handle ratchets; later ones had slot-in plastic ones..and on one side the suction pipe was attached.
I remember one week doing well with a couple I fixed on a local car boot sale; this was at a time when they were just becoming popular about 1990.
Early..and some replacement brush rolls were a pain, having a screw to remove at either end, sometimes seized in position. Some of the later Gen Electrolux ones had interchangeable ends for either Contour or 600 series machines.
As for the exhaust grilles, they were forever flying off! I did have a few second hand hoses but many disappeared with a 2004 garage break in. However, it's quite possible I still have a new one in storage and don't know where it's at! I've fixed a few myself, though it's a while since I've seen one; usually you can wedge in some screwdrivers to unclip the end, yank the remaining wire out of the screw thread and twist a new piece in. Some glue might help stop it working loose.
Stephen