Thank you both for the replies.
The device does have a static IP and when the issue is occuring, strangely I can still ping it but can't go tot he web or access the files.
As for the battery I can't say its status.
I was messing around with the power options of when to turn off the HD's after inactivity under Power Management and it was set to 30min. This was working in the past for sure as I could hear the 2 drives spin up after sitting for extended periods. I disabled the setting as a test and the issue has not returned. Not sure what has changed and why this is not working now. It seems once the HDs turn off they will not recover without a restart of the device. I have to pull the power as holding the power button doesn't turn them off like it use to.