@JohnKol I commend you for sticking around for 6 weeks all the while getting beat up. Trolls tend to lob a comment and then slink away to their parents basement. I don't think it is fair to call you a Troll. You put up with a lot of abuse. This discussion avoided me when it was volatile but I did read it in its entirety.
I've got a T5442TM-AS-LED that sounds like what you mention on your two cameras. Even though I could not access it, I knew it was online because this model has visible light LEDs. I could also see recordings on the SD card during that period. I did all the typical troubleshooting mentioned above and it just worked sometimes and sometimes not. At some point it was just easier to buy a replacement and shelf the old unit. I do still have it and will rip it apart when I have some time. Even the best things cannot last forever. This camera was in West Texas and it probably got really hot in its day.
Years ago, I had an ASTAK MOLE. ASTAK is now defunct but the MOLE was a good little camera in it's day. It was a P2P camera even though they described it differently and denied it was P2P. It went offline one time and since help tickets cost nothing, I put one in. They got it back online. When I asked what was wrong, they said it partially booted but they could see it on their end and rebooted it completely. I know they have to talk to the lowest denominator but having some linux experience, I imagined that the kernel booted and brought up whatever process that talked to them but the process that I needed to see the camera failed to load. Someone mentioned to reload firmware and reset to factory defaults. That is hard to do if you cannot access it. Before I retired the 5442 I just set it up to reboot weekly and hoped for the best.
The reason I read this thread was the title "Camera Reliability" I have a Dahua SD59432XA-HNR that had failed IR lights several months ago and an SD29204UE-GN that the IR lights failed last night. I was going to ask if there had been lots of IR light failures in the community. If there were, I would expect a material issue but if not, I would have to blame my specific situation. If a member says he has several thousand installs and had not experienced this it must be something local to my installs. Likewise, if a member has several thousand installs and only a few failures he would look at what was common to those failures. Location, production batch etc. In both our cases, they are different models maybe bought at different times so maybe unrelated.
So as I read the comments in this thread, I remembered that the 5442 had a similar failure as yours. After it had failed but before the IR lights, I had an electrical fault that cost me a television. My RV connection had high resistance connection and the plug overheated and I lost the common. It happened slowly but when I brushed up against the slide with my arm, I got a shock, slight at first. I could not repeat it by touching the same spot with my higher resistance finger. Eventually I could and I checked with my Fluke. I had 60 volts to ground on the RV frame. I powered down the rig and found the plug had melted. I essentially had 60 volts on the ground wire. The RV is plugged into a building which then also had 60 volts on the ground wire. The 59432 POE switch was plugged into the same outlet box as the RV. I lost it first. The 29204 I lost 4 months later. I believe they are related.
Electricity is fickle. Years ago, a friend got shock while in his pool. The power company verified this and several months later found a bad ground on a new construction house several blocks away. He stopped getting shocked after they fixed that.
BTW, I had Foscams in the beginning also. They were indoor cams and I had them hanging upside down outside below a frisbee to keep them drip free. They survived wonderfully considering the environment. I bet they would boot up today. But I would never by one again! I hope that you found a suitable replacement for your failed cameras!
Sorry so long guys!