Hi,
Apologies for not introducing myself somewhere else in the forum first. I'm pulling my hair out and I feel I need to offload before I can smile 
I have a number of fruit machines (90s and early 00s) which I have been accumulating and playing, slowly but surely. I keep coming up against some very similar problems which are incredibly frustrating, specifically with coin mechs. Any of the fruit machines that have not yet had their coin mech updated/upgraded for new coins including the new £1 coin work like a charm. No Problems. Anything I have which has an updated coin mech (and note that these are different mechs, upgraded by different people at different times) seems to end up having issues.
The most consistent issues are jamming in the mechs and/or then problems in the tubes and the hoppers. It is driving me insane.
Specifically I have just purchased a beautiful example of the 1996 Rocky Horror Show fruit machine. Was working fine for a good £200 of playthrough, set at 25p play and £15 jackpot. Coins going in fine. Payouts coming out fine. Lovely. Now all of a sudden I have a 'DF Error' which also refers to MARS Coin Mech Error and I cannot clear anything down at all. When I went inside the machine, I could see some £1 coins had started to collects at the bottom of the coin mech before coming into the tubes. I rattled them through so they sat in the hopper and this is now problematic. Error doesn't clear.
I'm a bit of a novice so I may be doing something stupid. I can see that inside the machine is a rotating hopper. I call it a magnum hopper because it reminds me of a magnum gun revolver bullet chamber There are 4 holes for the pound coins to collect and they are all full meaning that any excess pound coins will just sort of sit on top of them in a mess. I can see from the refill key that there is about £48 in the machine in total.
Am I doing something stupid or is there a universal issue with coin mechs? Frustrating 
Cheers
Justin