I believe I have a work-around, I had the issue, and I called a “Destroy Session” function right before the create session for the host, and it created the session as expected.
I believe is has to do with the multi-threading nature of the UE4, when it tries to delete the session it’s probably waiting on access from another thread, and it can’t get access to it, so it fails out. But when called before the creation, the NetController is fully destroyed therefor exiting out of all those resources held by those busy threads, so it probably doesn’t has that problem.
Again that explanation is a estimate, but I believe it makes sense.