XPS 13 9310 random shut downs

I have the unit plugged into a WD19TBS Thunderbolt dock and connected to a Dell wide screen monitor. 

When connected to the dock, the computer will randomly shut down. This happens after it goes into sleep mode and usually after it is in sleep mode for more than an hour. It's not consistent, but it is frequent enough that it's troublesome as any open apps are shut down with no warning. 

When the computer is not connected to the dock, it does not shut down and goes into sleep mode normally.

Any help is appreciated.