Well - more news no my disappearing cameras problem after a week of monitoring. I let things run for a while longer without any significant problems. Friday I decided to make a new group and camera arrangement. To do this you of course go to the camera settings, modify the group and save. When you save the camera settings the
BlueIris software appears to send a soft reset, or maybe more, to the camera, After about the 3rd camera all of the normal suspect cameras (Foscam FI89xxx series cameras) started going offline (lost connection & no ping response) again. This tells me that the suspect other devices on the network that were offline have nothing to do with the cameras going offline. It took me a while, but I did get them all back online by powering them all down and back up a few times, resetting the BlueIris server a couple of times and taking one more suspect machine on the bench offline. All started working well again for about 6 hours then the same cameras went offline.
Back to the shop to fight with cameras again Sat afternoon. This time all I did was power cycle all of the cameras again for them to come back onilne, last about 3-5 minutes then offline again. I went ahead and created the group and rearranged the cameras while the cameras were offline. Next step shut down the BlueIris service, power up all of the cameras and monitor the cameras with a ping test look and different (TinyCam Pro) software from one of my tablets. I let that run for about 30 minutes then started up BlueIris Service and shut down the TinyCam Pro monitor. I went to each suspect camera's video configuration settings while everything is online and had the BlueIris software rescan and reset the driver for the camera. They've been up for 13 hours without dropping offline yet.
Short answer, I am quite convinced that something in Blue Iris is communicating bad data causing the cameras to shut down until reset. This server and these cameras have been running without a problem for years on the older 5.4.9.17 software and didn't act like this until the upgrade. Of course, the group management funcitons weren't available so I didn't go through the same process with the cameras to set & reset cameras quite the same. Problem could have been on the older versions too, just didn't show up so frequently.
If anyone is interested, I'll report back on further findings. I'm really trying to not revert back to the older version. I'm a little disappointed that I haven't heard back from the Blue Iris support team (or guy).