v4.7.1 - have not upgraded as yet due to so many reports of apps and plugins not yet compatible and getting locked.
But for 24 hours, my queue task has been locked and background processes are all queuing up.
When I click Run Now, I get "The task is already running and cannot be ran until it has finished or the lock is removed." If I remove the lock, on its next scheduled run, it just locks again.
The only thing I can think of that triggered this was I attempted to move around 20,000 members from one usergroup to another, and in the task list that is currently sitting at 1.6% (after 24 hours), but surely other background processes can run simultaneously?