Not sure I would ship the box anywhere, but there are some things worth checking(assuming you have 2 BNC cables completing Loop Sync connections and the 192 has a Digital IO card in slot 3(IIRC, this is required). I would pull the unit out of the rack, pop the top panel and find the multi-pin connector on the Input card. Unplug it and do a thorough inspection of pins and sockets. Maybe hit it with some good contact cleaner and re-connect and test. If that makes no difference, instead of shipping the unit, I would just shop for a deal on another analog input card and replace the fouled card. If that fixes it, great. If that DOES'NT fix it, then you know its not the card, BUT, in that case, stick the old card in slot 4 and see if it works there(which might be worth a try anyway)