The basic problem was that this dimmer is wired with the one common wire looped between the output sockets. These are push-in connections and the stranded wire they use eventually burned inside the connector. Separate commons with screw connections would be a better design.
An open ended data cable causes reflections of the DMX data to bounce backwards toward the source. Terminators minimize the data being reflected back, which can cause fuzzy data transitions to cause problems in decoding the data.
The DMX-4 works normally for all settings in the chase mode but does not respond to DMX input. There is no LED channel activity when a known good controller is connected. I am familiar with circuit troubleshooting, but is there a schematic posted anywhere?