As soon as you start the conversation with Merlin, please spam the "Esc" key (or whichever button is assigned to skip cutscenes on your platform) right away, so that the cutscene doesn't get the chance to fully start. If the cutscene is prevented from starting, the quest step should be able to progress normally.
If this still does not resolve the issue for you, please don't worry — our team is currently working on it, and we'll make sure to keep investigating until a permanent fix is in place.