New qa.moodle.net "many questions" course is handy (thought the quiz there is strange: it is set to paginate every new question, but contains 5 question on one page as it is).
Enter there, press "Add random question" button on the end of the page (not in question bank) and see what's happens. I see a question added to this page and a new empty page added below, which doesn't seem correct. The behavour continues if you repaginate quiz: the new question get added to the page, breaking pagination rules, and an empty page is added too.
Some code on adding question to paginated quiz probably won't updated to catch up with an ability to add question to the particular page.