Have run into this with Swann DVR16-4000 and Digital Watchdog DW-VF960-162TB. Units record perfectly, except every so often they will skip 20-30 seconds (forever in event time!). Swann did not want to admit there was a problem, even after we had swapped out the unit twice and I sent them video clips. I never got a solution from them. I finally changed the recording resolution to D1 and this seemed to solved it. With Digital Watchdog as soon as I sent them a video clip they fessed up and within a couple of days they sent me a firmware update that seems to have fixed it. I think this is a through-put problem with the amount of data transferring to the hard drive at the 960 resolution rate with 16 cameras. Wonder if anyone else has encountered this problem? Also changing the resolution on the Swann unit did not degrade the recording because the cameras are only D1 resolution. Swann products are decent, but their Tech support (even at Advanced Level) stinks.