I can concur that
that firmware update works perfectly on the NVR5216-16P-4KS2 (hardware version 1,
not the 4KS2E) - problems such as cameras re-booting on motion detect, the NVR not being able to reliably communicate with the cameras, and general lagginess have all gone. Note though that the main Dahua web site no longer lists firmware for the 4KS2 - you'll want to go to Dahua's
European FTP site to get it (don't under any circumstances install the firmware listed on their main web site - it's for the 4KS2E with v2 hardware, and will very likely brick your v1 NVR).