Sorry to hear you are experiencing troubles with Method!
Would you be able to email me a screenshot of what your screen looks like prior to save? The address is firstname.lastname@example.org
Specifically what I am looking for is what Checkboxes on screen you have checked off. There should be two in the top right hand corner of the screen;
- Email Case notification to user when saving?
- Email Case notification to contact when saving?
And then one in the bottom right of the 'Case Dialog & New / Edit Activity' section;
- Email Activity notification to user when saving?
Which of these checkboxes (if any) do you have checked? The reason I ask is that the 'Action Sequence Order 20' part of your error message can refer to one of a few different actions behind the scenes depending on what you have checked off here.