The BBWR in the serial number suggests they are set as 'World Region'.
Out of curiosity - what drives the need to upgrade them?
Agree don't upgrade which I assume you think you need to because the versions are not the same. Means nothing just the browser page will look different but, I bet very little in anything with the functionality. If they are in language you can read and they work then don't break them be happy.
Thanks for answering guys!
Out of 6 cameras totally, I have problem with 2 of them (both on V5.3.6) I'm trying to figure out what's causing the problems and spent more or less the whole day yesterday to do so. The problem is that these two cameras loose their network connection frequently. When that happens they are not even ping-able. The interruption lasts for a minute or two. It's typically gets worse if I connect multiple clients to the camera. It's not related to the network cable or to PoE. (The problem has been seen while the faulty cameras was connected with a new short network cable to the switch at a non PoE port using an external power supply) I have tried to remove "smart events" from the configuration and it feels very much better now. The two problematic cameras both have V5.3.6 while the working cameras all have V5.3.8. It might be a coincidence and I'm aware that I'm grasping for straws here but currently that's the only thing that I've got... The Chinese vendor has offered to send me the V5.3.8 software by e-mail so I'm currently waiting for it.
If it's not the older software causing the problems I believe it's a hardware failure. I don't know really, what do You guys think? Isn't it worth to try?
Edit: I use
tinyCam Monitor PRO on my smart phone to view all cameras. The protocol used for all cameras are set to "Snapshot (JPEG)" If I change the protocol for the faulty camera to "RTSP over TCP (MPEG/H264/H265)" it seems more stable but the problem still arises occasionally. It's kind of weird... needs more testing.
Edit2: It's worse than ever this afternoon so I've tried to reset the configuration (all except IP and user id). It's still giving me problems. Using firefox to view the stream, substream 1 doesn't work at all. Substream 2 which has a lower resolution works.