Thanks @jonas . It was actually the other way around, I had HTTP/2 enabled for streaming and when I disabled it the Buffering issue did not appear.
With this setting disabled, it works in 1.2.5 and 1.2.7
It looks like a bug when using that config. Let me know if you want me to open a ticket for it or test further, for now I'll use HTTP/1.1 
Thanks again!