I also this one :
2022/03/01 18:49:46 [error] 609#609: *4 connect() failed (111: Connection refused) while connecting to upstream, client: 172.30.32.2, server: a0d7b954-nodered, request: "GET /null HTTP/1.1", upstream: "http://127.0.0.1:46836/null", host: "xxxx.duckdns.org:8123", referrer: "https://xxxxx.duckdns.org:8123/api/hassio_ingress/LoU-Cnl1bxSDwjOvkTlL95pACuS98Gs-PmK-zBQ2Hwg/"
Also had the same 502 Bad Gateway error since this morning. Seems NR just keeps rebooting all the time:
> node $NODE_OPTIONS node_modules/node-red/red.js "--settings" "/etc/node-red/config.js"
1 Mar 20:14:30 - [info]
Welcome to Node-RED
===================
1 Mar 20:14:30 - [info] Node-RED version: v2.2.2
1 Mar 20:14:30 - [info] Node.js version: v16.14.0
1 Mar 20:14:30 - [info] Linux 5.10.92-v8 arm64 LE
1 Mar 20:14:32 - [info] Loading palette nodes
1 Mar 20:14:36 - [info] Dashboard version 3.1.0 started at /endpoint/ui
1 Mar 20:14:39 - [info] Settings file : /etc/node-red/config.js
1 Mar 20:14:39 - [info] Context store : 'default' [module=localfilesystem]
1 Mar 20:14:39 - [info] User directory : /config/node-red/
1 Mar 20:14:39 - [warn] Projects disabled : editorTheme.projects.enabled=false
1 Mar 20:14:39 - [info] Flows file : /config/node-red/flows.json
1 Mar 20:14:39 - [info] Server now running at http://127.0.0.1:46836/
1 Mar 20:14:40 - [info] Starting flows
[20:14:42] INFO: Starting Node-RED...
> start
> node $NODE_OPTIONS node_modules/node-red/red.js "--settings" "/etc/node-red/config.js"
1 Mar 20:14:46 - [info]
Welcome to Node-RED
===================
1 Mar 20:14:46 - [info] Node-RED version: v2.2.2
1 Mar 20:14:46 - [info] Node.js version: v16.14.0
1 Mar 20:14:46 - [info] Linux 5.10.92-v8 arm64 LE
1 Mar 20:14:47 - [info] Loading palette nodes
1 Mar 20:14:52 - [info] Dashboard version 3.1.0 started at /endpoint/ui
2022/03/01 20:14:54 [error] 572#572: *3 connect() failed (111: Connection refused) while connecting to upstream, client: 172.30.32.2, server: a0d7b954-nodered, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:46836/", host: "homeassistantprod.local:8123", referrer: "http://homeassistantprod.local:8123/a0d7b954_nodered"
1 Mar 20:14:55 - [info] Settings file : /etc/node-red/config.js
1 Mar 20:14:55 - [info] Context store : 'default' [module=localfilesystem]
1 Mar 20:14:55 - [info] User directory : /config/node-red/
1 Mar 20:14:55 - [warn] Projects disabled : editorTheme.projects.enabled=false
1 Mar 20:14:55 - [info] Flows file : /config/node-red/flows.json
1 Mar 20:14:55 - [info] Server now running at http://127.0.0.1:46836/
1 Mar 20:14:55 - [info] Starting flows
[20:14:58] INFO: Starting Node-RED...
> start
> node $NODE_OPTIONS node_modules/node-red/red.js "--settings" "/etc/node-red/config.js"
1 Mar 20:15:01 - [info]
Welcome to Node-RED
===================
1 Mar 20:15:01 - [info] Node-RED version: v2.2.2
1 Mar 20:15:01 - [info] Node.js version: v16.14.0
1 Mar 20:15:01 - [info] Linux 5.10.92-v8 arm64 LE
1 Mar 20:15:03 - [info] Loading palette nodes
1 Mar 20:15:07 - [info] Dashboard version 3.1.0 started at /endpoint/ui
1 Mar 20:15:10 - [info] Settings file : /etc/node-red/config.js
1 Mar 20:15:10 - [info] Context store : 'default' [module=localfilesystem]
1 Mar 20:15:10 - [info] User directory : /config/node-red/
1 Mar 20:15:10 - [warn] Projects disabled : editorTheme.projects.enabled=false
1 Mar 20:15:10 - [info] Flows file : /config/node-red/flows.json
1 Mar 20:15:10 - [info] Server now running at http://127.0.0.1:46836/
1 Mar 20:15:10 - [info] Starting flows
[20:15:13] INFO: Starting Node-RED...
> start
> node $NODE_OPTIONS node_modules/node-red/red.js "--settings" "/etc/node-red/config.js"
1 Mar 20:15:16 - [info]
I believe that I found the reason 
Actually, thanks to @PickleSlice who gave me a clue with Node-Red addon. 11.0.4 version was release yesterday and in the issue log of the GitHub project there is crash reference with Serial port. : https://github.com/hassio-addons/addon-node-red/issues/1312
On my configuration, I have with a teleinfo module the capacity to monitor my energy consumption
This module is connected to my raspberry pi4 (that host HA) with an USB connector. But in Node-Red, I was obliged to declare a Serial connection in order to read my electric meter.
By removing the USB connector, I immediately retrieve access to NodeRed interface.
So, now, I have to wait for a new NodeRed module update.
I hope that my explanation are clear and can help most of you
Exact. I had the same behavior, and if you are in 11.0.4 version and use Serial port (even if it’s through an USB), remove it and normally you’ll retrieve access to NodeRed 
I’m glad that worked for you, but I don’t have anything like that unfortunately.
You haven’t any serial node or any devices connected on your serial port ?
No, nothing.
What’s happened for you today ?
Do you encounter the same behavior than me and juanh (constant restart of NodeRed ?)
@PickleSlice if you enable safe mode will it start? you could try adding the following to your nodered config.
init_commands:
- npm uninstall node-red-contrib-huemagic
If none of this helps, restart nodered, wait 2-3 minutes, go to the nodered log page and post the output. Also what type of home assistant install are you using.
I don’t think I explained it properly. My Node-RED addon launches fine, just none of my hue bulbs that I control with HueMagic are working.
Try removing the hue magic nodes from the side menu, manage palette, uninstall. Restart nodered then reinstall via the the palette manager.
I’ll give that a shot tonight when I get home, thank you!
I have the same issue and disconnect the usb until it is fixed 
The same problem with serial and RFLink.
I restored a backup I had, with version 10.0.1 and everything working perfectly.
I had the same errors. The problem was an esphome sensor (which triggers some automations in node red) which was having problems and changing state many times per second
I am having the same problems with Node Red as soon as I plug a USB to serial adaptor into the raspberry pi. It prevents access to Node Red. I have tried both FTDI and Prolific usb to serial adaptors. Within a few seconds of removing the adapter, I can access Node Red again. Everything else in HA seems fine. If I try using port 1880 whilst the USB adaptor is plugged in, I get the NGinx “Bad Gateway” screen - all is fine as as soon as I unplug the adaptor. Really annoying as there seems no other way to use a bi-directional serial link to an external device for use. Guess we will just have to wait. I don’t know how one reports this kind of problem.
Does the adapter work otherwise. Does it show up in HA? Have you tried to connect through it from H?
I am having the same issue with a Envi Cost serial interface, the port works fine using the terminal and receives data properly but Node-Red Serial component does not connect and does hang the interface. Removing the USB adaptor allows the UI to work again.
It seems to me the Node-Red Serial component does not have the correct privs to connect and hangs when constantly retrying!
I know it’s an issue with zigbee/zwave usb, they need to be extended away from the pie a meter or two. Have you tried with an extension cable?
I tried that, same. The fact that the Pi can see it and works using a terminal application tells me it’s purely the HA/Serial components at fault. -Thanks for that though