You still getting an issue with that? I certainly get that just fine when going through my NGINX proxy.
Yep - it seems to come and go. I haven't pinpointed anything that temporarily fixes it though. Every few weeks now I've done a bunch of updating node-red / updating nginx / restarting all the services... then in the middle of all that (not immediately tied to a service update/restart mind you) it'll just start working for a day or two, then it'll be back.
It's super fun 
Sounds more like a system performance issue. Time to check some parameters on the system. It could be that something is causing temporary issues periodically.
I use Telegraf/InfluxDB/Grafana to monitor my server but you may have some other monitoring in place?
I mean node red works... does all the node-redy things it's supposed to do. Interacts with home assistant and mqtt just great.
The labels are just not there -- not sure what to monitor?
CPU, Memory, SWAP and maybe disk use. Not sure if you told us what device you are using and how much memory/resources you have.
