As Harry mentioned, it seems that this is indeed a bug, as there is a KB that talks about it here. There are also steps that can be performed as a workaround, although settling for 5.2.10 is also an acceptable workaround.
Currently the reason this is happening is still unknown though.
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
We're bringing product updates and pro tips on teamwork to ten cities around the world.Save your spot