StepperOnline A6 Servos: Sync Error when closing LinuxCNC

Hi
I got tree Stepperonline A6 servo motors up and running in XYZ mode using the attached files. When I close LinuxCNC, however, all three drivers show error ErC 1.1, i.e. Sync Error. When I start LinuxCNC again, the errors disappear. So it is not a big deal, but it is ugly to see that the program was not terminated in a decent way. 

I suppose that there must be some appropriate commands in the shutdown.hal file. I tried a lot of things, but none of them worked. Dies anyone know what to put in the shutdown.hal file to prevent the sync error or is there an other way to prevent this error?

Thanks