Osiring NVR "forgetting" camera password

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Bottom line, the 48v poe injectors are fine. That's what your camera's looking for.
Maybe check the camera specs and be sure they weren't made for a lower voltage POE. I don't know how long 48v has been the standard. I suspect it came from phantom power for audio devices, which has been 48v for decades, but if you can check that's the prudent thing.
 
Just a bit of an update:

Cameras all have been working 24/7 since they are connected to a PoE injector (7 or 8 days now) (link). So, thanks for your suggestion, it appears indeed that it's a power supply related problem.

I still would like a solution to change the PW to admin/admin, as every time I disconnect and reconnect the lan cables, the original 2 cams (admin/admin) work immediately, the two new ones (admin/8 character PW) I have to manually input the PW.
If ever there's a power outage, the system will reboot and only 2 cams will work. Perhaps not that big of a deal, but it is an inconvenience.
For this, I tried manually hardware resetting the cams, accessing them through Pale Moon (doesn't connect to the ip address of the cam), the Dahua ConfigTool (doesn't allow a 5 character PW), and the SmartAdd function of the NVR (doesn't work at all). All suggestions appreciated!
 
Had the first disconnect in over 10 days. It happened at the reboot time of the NVR, so this is password related... I entered the PW, and everything works again immediately.
The osiris system was quite expensive, I hate to have to buy a new (NAS?) just for this reason. Is there anything else that I could try?