I just installed five new colorsource spots and noticed today that one of the lights will very occasionally and as far as I can tell yet randomly flash on then back off. The five instruments are all linked with dmx but each is powered separately. I have shows all weekend so I have removed the one instrument and will look at it again on Monday to see if I can see any commonality in the flashes but thought I would throw this out to the forums in case anyone has an answer.
If your system uses a lighting only network, you could try using ACN viewer and use the flicker finder feature. The software is freeware out on the web.