When I insert an image in the source interface, for instance [[Filename.jpg|800x800px]], and I save the page, then the image is displayed well. When I subsequently edit the text of the page in de visual editor interface, than Mediawiki adds <figure-inline> tags. The result in the source reads:
However, de tags remain visibly in the visible tekst when the page is saved. So every page visitor sees the text <figure-inline> on both sides of the image.
Besides, every next time I save the page in the Visual Editor mode, the tag is added again and thereby multiplying, so the result is a string: <figure-inline><figure-inline><figure-inline>etc.
The incident doest not occur when I put the image in a frame. The incident occurs after the latest Mediwiki update.