Zero space available - can not delete anything

I have filled up (zero bytes free) my EX4100 (firmware 5.25.124) using backups (Acronis True Image). I can access the “box” (e.g. console) via the LAN but can not delete shares to make room. Network drives do not connect so I can not delete any files.
MyCloud v5. I can not access via Mycloud either.

I contacted support who recomended that I connected to the EX4100 using an ethernet cable. They instructed me to disable Wi-Fi on my laptop, power down the EX4100 and Laptop, disconnect the EX4100 from the router, connect Laptop to EX4100 by the cable, power up the laptop then power up the EX4100. I was then able to access the dashboard and delete one of the shares so as to give me room. I then powered everything down, disconnected the cable, reconnect the EX4100 to the router and bring everything back up. After reconnecting the laptop to the wi-fi I found I had full access again to enable me to clear stuff out, recreate the share I deleted and re-fill it.
All is now well with the world.