If the entire rig goes into blackout at the exact same time, that's more an indicator of the console sending rogue signal. The way DMX works is it sends out a value to each DMX address sequentially. The light knows what channel to listen for and when it sees the signal, it sets itself appropriately, then waits until it's channel comes around the rotation again. If you lose DMX signal completely, the light will either remain where it was, or go to blackout mode, depending on how it's set. Each manufacturer and model of light will have a different amount of time before it gives up waiting for that next command. If all lights are blacking out in unison, that's unlikely to be the cause.
It's possible that mis-termination or a flaky cable could be messing with the data stream. However, usually this results in overall erratic behavior in the lights. Weird movement, random colors etc. For it to send blackout signal to all the lights as the only fault while not impossible is very unlikely.
The same thing with an instrument sending rogue signals. Usually those problems are more wonk than simple blackout.
Now, if your controller is getting cranky and instead of sending out the appropriate stream of signal and just sends out all zeros, well, that's going to cause all lights to go to zero immediately and in perfect sync. If the processor is overloaded and the console just doesn't know what numbers to send, that might be how it's going to react.
