We just had a very odd thing happen on our system - a user was working in a backlog and did a bulk change on 4 stories to transition them to a Done status. However, when he saw the confirm screen it said he was changing 34 stories. Seeing this, he immediately clicked cancel, only to find that the sprint these issues were on had now vanished from all screens (and the sprint report) and the stories moved to the backlog. When I looked into the database, I confirmed that it was indeed no longer in the AO_******_SPRINT table. Nothing appears in the activity stream for the user, and I am unable to recreate the problem, so I wondered if anyone else has seen this or something similar.
MySQL 5.6.35-80.0 (mysql-connector-java-5.1.39)