update: the machine is still driving me nuts. the drop sensor/chute is fine, not the problem. this machine has 3 depth settings, not 2 ... i can set it to single, double or triple depth (using 1, 2 or 3 in the menu) - all 10 selections are CANS but the front row is single depth, rear row is triple depth ... all of the depth settings are correct.
i checked the STS settings and they are also correct ... but the entire rear row will still not respond. it WILL WORK in 'test' mode .. but not sales mode. i'm having a hard time getting ahold of the tech guy at D&S Vending so any further suggestions here would be great.