This happens to me occasionally. Usually I can fix it by completely restarting Node-RED or HA, but that is no longer working.
It will stop letting me navigate to any flows besides the first. Every time I try, the whole thing reloads and goes back to the first flow.
I made a recording, but not sure if there is any way to share it.
Try connecting directly if you aren't already. Use the ip of home assistant but use :1880 instead of :8123. If you are asked for a password, use your home assistant user and password.
Not sure what this means? If you ment a screen recording to show what happens, have a look at ScreenToGif ... allows you to capture a full screen or the essential rectangle and produces a small animated gif which is allowed to be added to a post.
Constantly reloading might be a result from a defective flow which does kill node-red, the logs should tell you. Perhaps you could simply backup your flows file located in (the flows. json file)
/addon_configs/a0d7b954_nodered/flows.json
e.g. quit node-red, mode that file to a save place, restart node-red (it'll create a new blank flows file) and then use the burger menu (top right corner in node-red) and use import and use the file you just saved. It'll import all the flows without actually starting them right now.
You can then disable each of the flows and enable one after the other and check if the problem re-appears.
In case you recently added some 3rd party contribs you could also try to have a look at the folder
/config_addons/a0d7b954_nodered/node_modules
where all the actual active contribs are stored.
stop node-red
move the ones you recently added to a save place
restart node-red
The flows using the 'now' missing nodes from the removed contrib show errors since these are missing right now, but in case node-red doesn't restart it's likely one of these are part of the problem.
I have the exact same problem.
Started a few days/weeks ago.
Staring Node Red fine, also havent change anything for a while.
Flow 1 is fine, but it reloads when starting node red. Then 2-4 will crash everything back to first flow.
Update
Going to try a restore to Node Red 21.0.9 <- didnt help
Not sure what to do.
So.. I updated to latest Node Red, also 2 new Nodes. Nothing changed, still error but then i went into logs and it said nothing. Now all of a sudden everyting works. Did a reboot. Maybe thats it. I dont know 
This fixed it for me, thanks!
I had this problem recently, it turned out to be a browser adblock plugin causing it.
Thanks, this is likely what was causing it for me too.