I've been using my Promistreams packages in production code for quite a while now, including very complex high-concurrency usecases, and it has worked fine. I've tested it with very complex testcases, and that worked fine too.

And now I wrote a quick proof-of-concept for something using them, and suddenly that proof-of-concept starts exposing race condition bugs in my Promistream packages for a week and ongoing??

I don't understand software sometimes. Including my own.