This is a known condition relating to the need to sense a disconnected input trigger cable.  That being said, we should examine if this really needs fixing.  There is probably a reason you lowered the shutter controller trigger threshold and caused the shutter to be in a triggered mode for greater than 5 seconds, but is this essential to the operation of the IFO?

Many factors govern the operation of the shutter including: The ability to sense obvious configuration faults like disconnected input or output cables, anti-collision logic to prevent simultaneously driving the shutter up and down causing self destruction of the drive circuitry, determination of sufficient charge to safely fire the shutter, and others.  The point is that we should think long and hard about making a change to support an operational configuration outside that which is strictly required.