I know this is an old thread but was having exactly the same problem and was able to fix it by changing the rtsp transfer from Auto to UDP. Hope it helps someone.
This guy seemed to take a dislike to my neighbors car. Pretty sure he's the BF of the daughter that lives there as he finally is let into the home in the 3rd clip.
Glad to hear you found the issue. BTW I just checked the spec for your NVR and it's incoming/outgoing Bandwidth is 80 Mbps / 256 Mbps. The ports might be 100Mbps but the overall bandwidth is limited to 80 between all of them.
Its 100% the NVR doing this. Mine does it too but not to 32kbs. My maths might be wrong but I think HIK nvrs have 10mbps bandwidth 'port', so an 8 camera NVR can do 80mbps so is 16,384kbs not 16.3mbps? If you have less than 8 cams it's usually okay but if all your cams are >10mbps it seems to...