Hi,
yesterday we've experienced a curious behaviour after upgrading our production JIRA to v.7.1.6. We've used rapid upgrade method and everything went smoothly until final JIRA restart. We've finished updating all the plugins and re-indexing JIRA and finally we've wanted to restart JIRA one last time to be sure that it works as expected - it was a good decision because it wasn't working as expected 
After the restart JIRA couldn't start properly (well it started but no further than some "initialising operations", so nobody could access the system through the GUI) - there was no error in logs nor any explanation what was going on. The only thing that the system was doing was massive amount of operations on the database. Most of it was something like this INSERT:
INSERT INTO fieldlayoutitem (ID, FIELDLAYOUT, FIELDIDENTIFIER, DESCRIPTION, VERTICALPOSITION, ISHIDDEN, ISREQUIRED, RENDERERTYPE) VALUES (268502, 10703, 'customfield_11204', '', null, 'true', 'false', 'atlassian-wiki-renderer')
We let it work like that for about 3 hours but nothing changed in that time so we rolled back to the previous version from backup because our maintenance window was closing to an end.
Does anybody encountered such behaviour? For me it is strange that JIRA started successfully after upgrade and worked OK but after updating plugins and re-indexing it couldn't restart.
I know that it looks like a problem with one of the plugins but we haven't encountered it in our test instance so it was an unpleasant surprise for us 
