TYPO3 Core

Way to reproduce:

Setup a simple Textfield in Flexform in a custom cElement (havn't testet Plugin but I expact the same behaviour there)

   <settings.mytext>
                <TCEforms>
                    <label>My Text</label>
                    <config>
                        <type>text</type>
                        <cols>48</cols>
                        <rows>15</rows>
                    </config>
                </TCEforms>
            </settings.mytext>

Crete an Element of you type, save it. Now change text in the mytext field and just close the element. TYPO3 detects your changes and ask you to save or discard your changes (we all know this behaviour :-) )

Now add RTE to the field:

   <settings.mytext>
                <TCEforms>
                    <label>My Text</label>
                    <config>
                        <type>text</type>
                        <cols>48</cols>
                        <rows>15</rows>
                        <enableRichtext>1</enableRichtext>
                    </config>
                </TCEforms>
            </settings.mytext>

Do the same as above. The element just gets closed without any dialog and all changes are lost.