I do not believe that forge is compatible with vanilla, even if it is un-modded. This is mainly due to forge having different kinds of network packets as well as its own required client and server network handler that vanilla minecraft just doesn't have (although this networking should be done on a different named channel that forge's packets wont be being sent to if on vanilla). Forge might also add additional data onto some vanilla packets in some versions (which is just speculation, as I have never seen evidence of this before during my time modding, so it could be unlikely). There could be other reasons, but I would have to do some testing to find out exactly what is going on. In the meantime, I will try and find the right mappings to make your log file more readable, which should help get to the bottom of your specific issue here.
I will get back to you.
By
Jackson Perr ·