Hmm, yeah, that looks exactly like the issue I was thinking of. Maybe there's some edge case where it still persists.
I can't reproduce it though. Please save your path (e.g. the one in the video) and upload the the replay so I can try it on my machine.
Because it's little effort and I'll probably end up asking you to do so later anyway:
Please post the contents of the fml-client-latest.log
file inside the logs
folder inside your .minecraft
folder to some pastebin site and link to the post here.
Note that this log will only contain information on the last time you started Minecraft, not any previous runs.