FastAPI in dockerswarm fails to deliver responses over a few kilobytes

I have a FastAPI service that I deploy with traefik via docker swarm. Everything runs fine until I request an endpoint supposed to return a JSON file just over 10 Ko. The call to this endpoint take several minutes before returning an empty string along with a 200 status code. I've checked all the logs I could find, and it looks like FastAPI completes the request properly and instantly (thus the 200 status code). It should send the response to my traefik reverse proxy hosted on a different node on my swarm, that would forward it to the client. However it looks like the response is lost somewhere on the way, and the client never get the expected JSON file, and gets an empty string instead.

Has this ever happened to you ? Is there a parameter to set for docker swarm networks to be handled this kind of data (it doesnt seem that heavy to me) ? Any help would be greatly appreciated, thanks a lot !

I tried changing the endpoint name, deploying the service with standard docker and traefik (it works perfectly), returning a smaller JSON file (works well with very small JSONs). I'm out of options

To answer my own question - If anyone stumbles unto this: this was caused due to the GCP infrastructure hosting my swarm.

The VPC provided by GCP had a MTU (Max transmission Unit) of 1460, where docker network defaults to 1500. The package sent to my reverse proxy was thus dropped as soon as it was bigger than 1460 bytes.