I bought a couple of old second hand Clenport M84s knowing that there was a jamming issue with them that I would need to sort out. The problem is that as you turn the drum to the position where the pot drops the steel bolt at the back doesn't always drop down enabling the drum to keep turning. In a normal sweet/Pringles tower this is resolved by turning the coin mech handle a fraction of the way back/anticlockwise and the bolt drops but in the M84 the coin carrier in the mech has turned to the position that the little pawl (to stop reverse vends) has engaged and stops the handle from being turned back even a fraction so the coin mech is in effect jammed.
Just wondered if anyone had any experience of these machines as I suspect I may have to replace the drum but because of the design of the machines that will involve drilling a lot of rivets out. It's an old machine but basically the same as the M70 that Clenport still sell.