The Lighting Controller

I am using the d512 interface, with showexpress and running a chain of 3 slimpar56's followed by 2 slimpar 64's, then another 3 slimpar 56's (8 lights total). The lights are labeled d1, d8, d15, d22, d29, d36, d43, d57. Despite the fact that that no shutter command is given, my seventh light ...