Hi Jay,
Its suggested not to use all 4 ports. I believe the on-board transformer is not large enough to handle the current required. Ver 2 of the splitter now only has 3 ports on it. It can cause flickering and in some cases a ssr4-dmx not to work. I think it was talked about in the ssr4 forum last year.
The above info is just from memory and I might be wrong about the current and transformer.
Rick R.