Try restarting the health_index probe.
Look in the health index log for details of the error. Might need to increase the log level to 3 or maybe 5.
Are you using the health_index data? If not then you could just empty both the health index queues ( in the hub gui).
That will give you the space back, but if the queues start to build again then you will need to investigate why the health index probe isn’t draining the queues.
Cheers
Rowan