When adding a single code plugin sectin onto a WYSIWYG page, everything is parsed and highlighted correctly. When adding a second code plugin section to that same page in the WYSIWYG editor, the first code plugin get "destroyed" - the XML tags in the code plugin etc are converted to &lt; instead of <
This old mailing list thread describes the problem: http://tikiwiki.1073613.n5.nabble.com/Tiki-devel-Parser-problems-with-wysiwyg-td10967.html
Apparently this has not yet been fixed with Tiki 9.6
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