Just a shot in the dark!
If your using the hard wired ethernet connection simultaneously as well as the WiFi on the camera. I'm guessing the WiFi will be disabled? Try disconnecting the ethernet, reboot camera and see if you can login to the static IP WiFi address of the camera.
Indeed try H264.
H265 is not a efficient standard, apart from saving storage. It's compatibility alongside the not so smart + codec is likely to cause the issues you have experienced.
I would personally advise to use H264 and definitely not the so smart "+" codec on.
Also crank the bitrate up as much as possible via constant not variable.
You should be able to have one IVS rule for a tripwire and another rule for intrusions. So rule 1 is a tripwire and rule 2/3 intrusion, or similar configuration. Then subscribe to your required push notification.
Crazy that you have to complain about a service or product because of no assistance from a manufacturer/seller. Then post on a separate internet site for assistance for warranty.
Hopefully all works out for you.
Can I ask when the remote access was not available please.
Another thread from a trustworthy forum contributer has suggested the P2P servers/services has a possible issue.
I'm guessing a bit!
I suspect your network settings on the new router and configurations do not match the DVR. Is the P2P still active and online via network settings on the DVR?
Have you checked that P2P is still active and "online" via network settings on NVR. Also in network settings check DNS preferred 8.8.8.8 and alternative 8.8.4.4?
My initial thoughts would be that your Home Assistant software is causing the problems described. Other software will most likely never integrate correctly.
Have you isolated the Dahua camera away from the Home Assistant demands, to see if the problems resolve?
Motion detection activation should be active on each individual camera, separately. So to hopefully push the settings from each camera, after your update and reboot the NVR.
A firmware update is unlikely to resolve the problems with recording via motion detection. It's more likely down to user errors.
Please elaborate on the exact problems.
Sorry I'm foggy again.
You state: "It would be great if one could get this page during playback, so one could fine tune the settings. But I don't think there is a way." Then you state: "That part is not the problem".
Sorry but you seem to be asking a question in a convoluted way, then expecting...