Servo issues

[dwp102]

Help!! Has anyone else had this problem...my servo, (ko rsx2) will start the race correctly centred with the end points correctly set. And then by the end of the race its centre point is off some 30 points on the sub trim on a sanwa transmitter. I have tried a different transmitter and the problem is definitely the servo. I have checked the gears and nothing is broken Has anyone else encountered this problem? And if so what is the outcome. I am running a KF with alloy everything so am wandering if the issue lies with too big an impact doing something to the servo. But everything works fine at the start of the race. Any input would be most appreciated. Thanks.