Hi @michmzr, welcome to the community!
Your nginx config looks good to me, I have actually used a similar one in the past without problems.
So I am not sure this is actually a problem with the SSE approach of passing data from the server to the frontend. You can, however, easily rule this out as a possible cause by switching to websockets.
If that’s not it and seeing this thread is several years old, perhaps you can open a new thread specifying exactly what you’re doing when running into the “connection lost” problem?