Live preview on multiple instances?

[itekhi]

Hello!

I have issues with live preview when I run multiple instances of Payload with Next's cacheHandler configured (@trieb.work/nextjs-turbo-redis-cache in particular) (I'm running multiple instances in Docker using deploy.replicas)

I will explain the issue (I did not create an issue because I don't get how to create a reproduction URL with multiple instances & Redis cacheHandler, sorry...):
When I open any admin page edit, live preview works (admin bar has "Exit preview mode"), then after making a single change to any input, live preview frame is reloaded with the change, however the "Exit preview mode" disappears, and live preview no longer works :(
After reloading the admin page, everything is the same... (I believe sometimes it doesn't work even after reload, and sometimes works again for a single change, I will recheck that).

I think this looks like after change, live preview reloads the frame, and the frame gets routed to other instance of Payload where live preview can't work like that, between instances...

I wonder if I even need multiple instances, or should I just run a single payload instance on a machine, without Docker?
I'm concerned that the images seem to load slower (as if sequentially) when running only one instance. Is that correct? Or node server.js is able to handle multiple requests at once?

[itekhi]

So I configured multi-instance again with Redis cache handler, and re-checked what is the behavior.

And so it's pretty strange... When I open admin for the first time, admin bar shows that preview mode is active, and as before, after a single change "Exit preview mode" in admin bar disappears, even without the change applied :[
After page reload preview mode is not active even for the first time... And sometimes works "one time" again only after all instances are restarted...

I also started getting this error when I reload the admin page (no error when only preview frame is reloaded):

[20:29:44] ERROR: Not found
    err: {
      "type": "g",
      "message": "Not found",
      "stack":
          g: Not found
              at q (/app/.next/server/chunks/4547.js:189:41157)
              at process.processTicksAndRejections (node:internal/process/task_queues:105:5)
              at async f (/app/.next/server/app/(payload)/admin/[[...segments]]/page.js:132:7770)
              at async w (/app/.next/server/app/(payload)/admin/[[...segments]]/page.js:190:12429)
              at async x (/app/.next/server/app/(payload)/admin/[[...segments]]/page.js:190:16507)
      "data": null,
      "isOperational": true,
      "isPublic": false,
      "status": 404,
      "name": "g"
    }

Update:

I now confirmed by scaling down to 1 instance, that issue is not in cache handler or live preview installation, but in the multi-instance :/

So I guess the only thing is that the live preview doesn't work between instances... How can this be solved?