D-1 error

Hello I am getting an intermittent D 1 error on our J26 XPI centrifuge. It seems to happen more at the end of a run or when it is slowing down. I may run it 3 times and no problem then the error pops up. I know I need to replace the motor mounts and vacuum hose but after calling Beckman I get the standard call for service. Is there a particular board that gives issues or possibly bearings in the motor. It seems to spin freely but I will know better when I pull the huge buckets and shroud rotor off the spindle. They want 3k to take a look at the issue with no cap on the repair. Can anyone help me run down this issue. I am pretty good with a multimeter and have replaced transistors and caps on other centrifuge boards along with rotor bearings to get them up and running again. Thanks Chris