I hope there are others experiencing this issue or have experienced and resolved it; I have tried to find what is causing it, with no reward for my effort.
When creating an Email within Dynamics CRM 2016 (Online or On Premise) and clicking the Save & Close button, it only saves the record. In fact, the form doesn't really show that it has been saved. The only indication you receive is the Subject in the form header is updated. Clicking Save & Close does not actually close the form.
By clicking the X in the top right-hand corner, a message pops up: "Your changes have not been saved. To stay on the page so you save your changes, click Cancel." By clicking OK, the form closes and the record is displayed in the Activity view, correctly.
Now, when I reopen that Email activity and click the Save & Close button again, it works as expected: saving and closing the record.
Can anyone help me find out where the issue can lie? Thanks in advance.
Additional Notes:
There are not any workflows associated to the entity, either registered on or associated by having to create an Email activity.
There are not any plugins registered to the Email (or any Activity) entity.
There is not any JScript registered to the entity or any fields on the Email form.
There is not any custom buttons or custom JScript registered to any buttons on the Email entity ribbon.