JFire,
The camera could tell the NVR to start recording for 1) simple MD or 2) "Smart Detect", eg: line crossing.
#1 is supported by the NVR. The NVR understand the "MD event" message from the camera.
#2 is not supported by the NVR, unless it's the new 4K variety. (note: this is what my dahua distributor tells me. However, your results indicate it just might be supported somehow)
I'd like to understand how you accomplished #2 with your non-4K NVR. Then I'll use your solution in my system.
Allow me to test a hunch.
Did you have simple MD enabled and "Smart Detect" line crossing enabled simultaneously?
Simple MD could have triggered your recording. Line crossing may have activated also. But coincidentally.
So the question might be "What really triggered the NVR to record?" Was it MD or "Smart Detect"?
My camera is set up to send emails & snapshots for line crossing. The email subject line contains "Dome".
My NVR is set up to send email & snap for simple MD. The email subject line contains "NVR".
When I get a text & snap, I know what caused it, ie: MD or line crossing.
In your case, maybe the past recordings were initiated by simple MD.
You had Tripwire enabled, and maybe you gave credit to Triwpwire for the recordings....
I record 24/7. You record after an event. I don't know if there is a title or embedded text you might enable, so you'd know what initiated the recording....