Comment draft persists after submitting

I've been experiencing a strange behaviour on GitLab.com since the last deploy, so 10.0.0-rc2. When I submit a new comment on an issue the text gets posted but the draft persists. Below a couple of screenshots to better explain.

Screen_Shot_2017-09-15_at_10.00.20

Screen_Shot_2017-09-15_at_10.00.30

My browser is Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:55.0) Gecko/20100101 Firefox/55.0