Try this:
Add an Expand macro to a page. Within that Expand, add a Code Block macro and select "Collapsible" in the object properties. Make sure you've got some text within and without both macros.
Here's what I've seen on two separate computers (both using Firefox but different OSs):
Select the link for the Expand macro, there's the content including a code block that simply shows a link for "Expand source"
Click Expand Source, now the entire Expand macro (not the code block macro!) collapses although the pointer next to the outer Expand macro now points down, indicating the expand is open.
Click the text for the Expand macro again, and the code block is now displayed correctly, although the expand macro position indicator toggles into the wrong position once more.
For extra fun, put multiple "collapsible = true" code blocks within your expand macro and try to view them all.
