sega club kart problems-fixed then something else goes wrong

[grantspain]

two reasons i'm posting this,as a guide to anyone googleing with the same fault and also because i'm really peed off.
o.k so my company has 2 club karts linked and since they bought the machine 2 years ago it would lock up on credit insert every now and then(maybe once or twice a week),so i check all the usual-voltages,connections,link cable and swapped the naomi boards to see if the fault was on one machine only-nope still the same,so i sit there thinking(whilst smoking a ciggie)what are we doing wrong because every other club kart in the world ain't got this problem-then it hits me,we have our machines set at 2 coins 1 credit and the credit board set at 1 coin 1 credit,the machine locks up at the second coin input always-so i set the credit board on 2coins 1 credit and the machine at 1 coin 1 credit,3 weeks on no lock up faults,perfect
well i get in to work today and the machine is switched off with an out of service label,so i now check the machine and i have error 22 comunication error between option and main board,turns out to be the game rom board(back to u.k for repair)
what i'm trying to say is machines have brains and just when you think you've beaten/fixed one they throw up a fault like this