I have never had the error if I open the shutter via MaxIm or TSX, and then use the ACP StartUp script to complete the startup. I don't get the problem if I close the Shutter in MaxIm or in TSX.
This is an important hint. It means that TSX and MaxIm are ignoring the shutter status indication and just sending the command in the blind. ACP, having been designed to be used without a person present and looking at the physical device, takes the position that "any error reported by the device is an immediate failure". The idea is to do its best to protect the equipment against further damage. The shutter should not be reporting an error unless it is in trouble.