In my setup if I use the break or any other tag in the marker it gets stripped as soon as I save the changes or refresh the preview. I don't have any problems using tags elsewhere and trusted content is enabled. I can create a question on a different moodle setup containing a break tag then export and import and all is well...until I edit the question and then, once again, the tags are stripped. I cannot find any setting that affects this behaviour. Am I missing something obvious?
Upgrading the OU quiz modules from 1.3 to the latest 1.8 seems to have solved my problem.