If you are creating a notice and choose the wrong module or do not choose a module (acquisitions module will default) - set up the Message Subject, Message Name and add content to the notice. Once you change the module- the page reloads and all information will be lost at this time, This functionality is currently in 18.11.03 and also seen in Koha 18.05.08 This is similar to bug 14358.
*** This bug has been marked as a duplicate of bug 14358 ***