Why would the code #8 transfer switch failure keep appearing at random times on the 30kw liquid cooled generator.

I have check the fuses each time in the automatic transfer switch and they have never blown. I have check the dip switches and they are set for 27kw because this generator is operating on natural gas. This problem seems to occur when it is either trying to exercise or when it is shutting down from exercising. It doesn't happen ever time either. I checked this right before hurricane Irene and it was out on Code #8 so I pulled the fuse on the control panel on the generator to clear the code and then reset the exercise clock. It came on for power failure and ran perfect for 2 days until the power was restored. Then i went back a week later and it was off on code # 8 again. This is very frustrating any ideas would be greatly appreciated.