Hi Nick,
I'm sorry for the troubles! We are aware of this issue and we are working to get it solved as quickly as possible. You can use the Drag and Drop editor or the Custom HTML editor to avoid the problem if it is affecting the work on your template. If you are using a template you have already created, you could clone it and make it a Custom HTML editor.
Sorry for the inconvenience and we'll get it back up and running correctly as soon as possible!