This is typically caused by the alt text field of the image that is being uploaded.

If the alt text field contains special characters, commas, quotation marks, etc. it may not insert in the slideshow part.

Recommend removing the alt text from the image and try to insert it into the slideshow part again.

After the image has been inserted in the slideshow without the alt text field containing data, the image can be edited and the text can be added without issue.

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