Not sure what to do

Here we go. Years ago I built a bundled firewood vending machine. About 5 years ago I finished it. I had purchased a used Mars TRC 6800 H coin changer and a Mag Pro mag 30 sa bill validator, 110 volt. I set it up for a $5 vend, accepts $1 & $5 bills only, does not give change, does not accept coins. All had been going smoothly for about 4 1/2 years, until about 4 months ago. The bill validator stopped accepting bills. I tried to fix the issue to no avail. I sent the bill validator out for repair to Coin Co in MD. They said they replaced a harness and cleaned the sensors $125. I reinstalled and still no bills were being accepted. I then brought the validator to a repair facility in Milford CT. $25 for a bench test and they it was ok. Reinstalled and same issue. I checked and rechecked all wires and connections on the coin changer and bill validator as well as through out the machine. All seemed good. The bill validator still would not accept bills. I contacted a guy in RI who said he would take a look at it. I towed to him and after approx 1 1/2 hours he could not get working. He then tried one of his spare Mars bill validators and the machine vended as it should, however each time the bill validator accepted a bill the coin changer tried to dispense change, but the machine did work $80. He said he had a refurbished Mars VN 2500, which I picked up the following week $200. Installed the new bill validator and the machine worked except the issue of the coin changer dispensing coins each time a bill was accepted. I emailed the RI guy and he asked me to check if I knew what coins were being dispensed. At that point I was not sure. I left the machine as is for the last 6-7 weeks and it had been working along with the coin dispensing issue. I lost a lot of business over the last four months while trying to figure things out. Yesterday I checked the machine, it had sold 3 bundles and when I unclipped the cash box the red led was flashing 2x - disabled front system-. I been the only one ever attending the machine, so no switches or any thing else were touched or changed. I checked the wires and connections as well as the level of the coins in the coin columns. All checked out ok. I forgot to mention the coin changer sits on a shelf so in the last 6-7 weeks I have not had to add any coins to keep the levels up. I bought a refurbished Mars TCR 6800H coin changer today, from the place in Milford CT, $130, installed it and still led flashing 2x and not accepting bills.Price was set to correct price,$5 and #4 of options bar on(BA HI/LOW) all others off. I turned power off and set #5 on options bar to on all others off. I inserted a $5 bill , it was accepted and I completed a vend (still with the coin dispense issue). When I checked the led, steady red, thank GOD! I then inserted 5 $1 bills and completed a vend (still with the coin dispense issue). When I checked the led on bill validator flashing 2x and bill validator will not accept bills. I check what coins were dispensed and it appears each time the bill validator did accept a bill the coin changer dispensed 1 each, quarter,nickel and dime. This is where I am at any help greatly appreciated. John