Weird blinking

My EX2ultra upper led start blinking slow after not using the cloud for a while ,
and a warning window “network cannot access ex2ultra/public/pictures” (depending the folder I was last in).
All is fine except this.
Start to happen after last firmware update.

Clues?

NAS automatically goes to sleeping mode when not in use for some time.
Takes few seconds to wake up again.

Check and disable this feature through SETTINGS/ENERGY SAVER/DRIVE SLEEP menu of DASHBOARD.