It probably means something is going on with the queues sending data through Splunk. I would check metrics.log for messages that show 'blocked=true'. Disk space could be part of the reason you'd run into this issue, but its sort of a generic 'things aren't healthy' message.
What did it end up being?
I am having the exact same problem and have ample disk space as well. I do find a lot of "blocked=true" in the metrics log but not sure how to remedy. what ended up working?
How was this resolved? Please help