When trying to decommission storage nodes, the progress automatically goes on pause.
From GRID Topology > Primary Admin Node > CMN > Tasks:
The Storage Node decommission cannot complete. Ensure all nodes are running and connected. Then, review all Erasure Coding profiles in use to ensure they can still be fulfilled. As required, update the ILM policy and try again. For details about this error, check bycast.log.
From the Decommission page it reports:
Decommissioning Erasure Coded Data