JCE is slow on loading articles which contains more images and hyperlinks behind those images.
This was earlier no problem but now I have to wait several seconds before I can edit such an article.
In the front-end there is no problem with those articles.
Other articles are loading fine
EDIT: In the 'Editor Global Configuration' section you can choose Custom CSS Files and add more than one css file (image 2). But when I choose the theme.css and my own custom.css this behaviour occurs. If i load only my custom.css it's working fine but then I'm missing my template css styles.