I had some Din Unlock issues with the DR 100mkII as I was setting up for a show. For me it was a bad S/PDIF cable and I have since replaced the cable. If I jiggled it, It would unlock but as I recall it would relock with more jiggling, I did not have to start or stop or re-start the deck. And yes if it is incompatible with a device you get the exact same message, but because this was not your issue, I would suspect the S/PDIF cable but perhaps it may have been a temporary loss of power to the V3 with its power cable being jiggled? Hard to say but you may want to try to recreate the problem focusing on those two areas and see what happens.