Brother PC 8200 repair?

Embroidery machine constantly goes berserk and starts breaking needles. Just came back out of repair shop Tuesday, lasted less than 5 hours of operation. At wit's end. Repairman says timing off a little every time I take it in. What is he not doing that makes it lose it's correct position? Is he not tightening something down enough? My husband could repair it if I could find a trusted place to download a service manual, he repairs high end appliances for a living. Any info appreciated.