On the mobile site, Safari on iPhone
https://english.stackexchange.com/search?q=test
Clicking on the page 2 button or next button takes me to
https://english.stackexchange.com/search?page=2&tab=Relevance&pagesize=15&q=test
which is just a blank search page
Looks like the & is being double-HTML-entitied. Only tested on English and Stackoverflow, worked fine on the latter but not the former.