Sorry, there was a problem with our issue tracker. In a few words, anonymous users could not search for issues even though they could view them if they typed their URL in the browser (like awnaba.atlassian.net/browse/PCP-221). This was confusing ( to say the least) and spoiled one of the main use cases of an issue tracker: finding if someone has already reported the same issue you are experiencing.
After finding this was caused by the bug JRA-38511 (thank you Google!) and applying the workaround described there, now everything is working again.