Nighthawk R6400 - Connected Devices Shown With Dash (-)

This is an update... After several months, I have finally resolved the issue. I believe that all of this is the result of too many devices being simultaneously connected to wifi on the router. At least to the 2.4Ghz channel. I do not know for certain what the limit is or if it is a function of the hardware or the firmware. I have read many posts in many places and the number is unclear. But there definitely is a point at which connections just start to drop. Note that this was NOT a throughput issue as most of my devices as IoT or smart home devices and really transmit very little information. The router is not really giving any warning of this but the dash (-) may be an indicator.

Netgear was helpful to some extent in my resolving this problem. The sent me a v2 of the R6400 in hopes it might just fix things - kind of an experiment. After some initial testing I discovered that the connected devices UI in the v2 was so different that there was no way to compare apples and oranges. So I just started stress-testing, adding every wifi device I could put my hands on - most on the 2.4Ghz channel as they were older IoT devices that can only use 2.4Ghz. It soon became clear that there is a limit and that even though the v.2 box clearly states "supports 25 devices", I was able to encounter problems at about 17 wifi devices total.

In doing more reading, I decided to try re-purposing an old router as a 2.4Ghz wifi access point wired to the R6400. This is not ideal in that it introduces a new SSID into the mix and I had to find another clear channel to use. But it has definitely helped a huge amount! My wifi load is not split across the 2 SSIDs/channels and all of the devices on the access point appear to the R6400 as wired devices, not wifi devices. I was able to reach a total of 29 devices connected (from the R6400's point of view) without any problems at all. At least 10 were devices connected to the access point, 3 were directly connected to the R6400's switch ports, and 3-4 were on the R6400's 5Ghz. The remainder were on the R6400's 2.4Ghz.

I also started looking into a possible new router that claims it can support many more devices. Such claims are becoming more and more visible in the marketplace and this makes sense as more and more IoT and smart home devices are being used. But none of the routers I found clarified the details of the device limit. For example: (a) is it a "hard" limit or somehow "soft" and variable based upon other conditions, (b) does the limit apply to all connection means taken together or is it per connection means (ethernet, 2.4Ghz, and 5Ghz), and (c) what does the router do when the limit is exceeded (is there some explicit warning, are new connections simply refused, etc). Given these uncertainties, I will just stick with what I have now for the time being.