I understand the concern. Although I have 2, this is actually in an apartment. One is within arms reach of the primary sensor I'm having the most issues with. Another is on the other side of my closet / around 3-4 feet away.
If I add another in this case, it would be on top of the one that's already installed.
Edit: 850 Square foot Apartment. Hue hub is centralized. I'm not dealing with much space here.
Totally agree with your comments. I spent quite a few years designing / deploying wired and wireless networks for large congested hotel / conference centers and you're bang on with best practices.
I can usually tell if wireless interference is happening because all the Zigbee devices in that section of the house will behave somewhat the same. It'll manifest in lights from time to time as well. This seems to be something different because my bedroom motion configuration is ignored until I remove it / replace it.
Metal studs in the walls?
If you're using 40 MHz wide channels, consider using 20 MHz wide channels.
Just another thought…. 
Are your Hue motion sensors running the latest firmware available for them?
Totally understand the concern about wireless congestion, and to be truthful that's the first place I go when I'm troubleshooting my setup. What doesn't add up (And why I checked in here), is why I'd see the device active and registering motion active/inactive without the scene triggering in the one room.
I can even manually trigger it using voice when it happens. It won't start working again until I delete the entry in Motion app and recreate it.
We need more data here. I thought your earlier message to @ogiewon indicated that the scenes always triggered when the sensor was "paired".
But if it doesn't then, can you post a screenshot of logs? The scene is presumably using bulbs brought in via your Hue bridge?
I actually was wondering if that could be causing issues too. These hue motion detectors have never been paired with my hue hub, and I don't think Hubitat pushes Hue firmware to the Hue motion detectors paired directly to the Hubitat.
Whatever firmware they're running I can only assume is the firmware they came with in the box. I'm assuming I'd need to remove them from Hubitat, join them to Hue - update them and then remove the from Hue / rejoin them to Hubitat.
It's just odd when they aren't going unresponsive, I'm seeing issues of them registering active/inactive in Hubitat without the Motion app triggering.
It can. As of platform 2.2.7.x
Two behaviors to avoid confusion:
I'll be out today, but I'll try to find some logs that might help.
I'm assuming the "Update Firmware" button in the device entry should do it? If so I'll run it on each.
Edit: 3 out of 4 are running old firmware. I'll update the firmware on all 3 and let it bake for a few days to see if anything positive happens. That could very well be it.
I've got one close neighbor with a constantly-hopping access point and another with one 40Mhz wide 2.4Ghz channel right across two of the standard wifi channels. My Nest Protects, poor things, are on and offline like jackinaboxes. We're only just about surviving, signal wise. But it's hard to select a channel when the neighbors can't make up their minds 
I'm going to take a shot. You mention living in a congested area. Is it possible you have neighbors with zigbee devices?
You could try changing your zigbee channel. You mention your setup been stable, so I'm thinking something else has changed, besides firmware. Check if your PAN ID has changed on HE
see this thread;
Hi all,
I absolutely appreciate the help. As I mentioned previously, I do come from a professional wireless design background. That's not the issue. I know wireless interference to see it, and this wasn't it. My setup (Including 2.4Ghz and 5Ghz) has been planned around absurd levels of wireless collision from day 1. It doesn't just happen sometime here, it happens constantly. I'm really familiar with what it looks like and the behavior.
After updating the firmware on 3 of the 4 sensors the issue hasn't repeated. It seems it was a case of old firmware on most of the sensors.
Thanks again for all the suggestions. This is resolved!
Edit: For anyone else trying to update Hue motion detector firmware through Hubitat, I recommend placing the motion detector you're updating on top of the hubitat hub while it's updating. Otherwise it'll fail repeatedly. Also, only update 1 at a time. They take a very long time.
Must you be using native HE Hue Hub Integration in order to do update firmware from the device screen? In other words, must HE be connected to the Hue bridge natively or just the device needs to use the Hue driver from HE?
LJ
This. I joined mine to the Hue bridge temporary just to update prior to pairing to HE, but @aaiyar has mentioned updating them over HE I believe. I think he recommended bringing them very near the HE hub for receiving the update. FYI: The update is very slow on Hue as well.
@aaiyar I must have something set up wrong then. I have a number of Hue Motion sensors I have brought one of them right next to the HE. When I press Update Firmware nothing happens in the logs. Ever. How long is a long time. I have waited 30 Mins. Does the update get logged?
LJ
Here's what I did:
The process can take 10 minutes to several hours, but you should see things in the logs immediately. The logs will come from the Hub not the device (so look for sys:1)
This thread has a lot of useful zigbee firmware update information (including about Hue motion sensors)
Download the Hubitat app
