Disk storage goes offline and then back online

I have multible backups destined to disk storages which are defined using network shares of NAS device (Fujitsu Celvin Q802).

From time to time these disk storages goes offline and then after few minutes they come back online again. There has been no BE backup activity at times when this happens. There are no other errors in windows system logs either, only this BE allert about "Device is offline....".

I am wondering:

• How does BE 2014 determine when disk storage is offline / online?
• Can I tune parameters related to this somehow?