[TYPO3-english] Empty Alt-Tags in images (4.7.4)

[Torsten Bahr]

Hi,

I'm working the whole afternoon on a strange problem, now hoping that you can help me. I updated an old 3.8.1 installation to 4.7.4, what worked great except one thing: The text which I enter in the "accessibility-fields", like "alternative text", which are supposed to be added to the alt-tag, are not shown in the FE. 
I don't know if this has something to do with it: In 3.8.1 the extension dmc_image_alttext was installed, as here two additional fields for alt and title had been added to "Text w/ image" and "images only". In 4.7 (and earlier) this isn't necessary anymore, as the feature is already included.
But no matter what I tried, the alt-Tags are always empty. 

css_styled_content is included, of course. 

Any ideas?

greetz
Torsten