Question: When working I will have multiple windows of file explorer open at a time. If I than start working on something else and leave those windows open in the background, they will close themselves leaving only one of them open. I have tried going into task manager and restarting file exploiter and that didn't fix it. i am running Windows 10 pro. Does any one have any ideas on how to fix? 

Thank you!

Answer: 
The simple fix is to set the Drive Map GPO to use the Action UPDATE.

To stop your mapped drives disappearing or automatically closing:

Launch Group Policy Managementnetwork-mapped-drives-closing-spontaneously-automatically
Find your drive mapping GPO, right click on it and select EDIT
Expand USER CONFIGURATION > PREFERENCES > WINDOWS SETTINGS > DRIVE MAPS
Double click on the drive map that is automatically closing
Change the ACTION drop down from REPLACE to UPDATE
I've had some users complaining about this happening.
After seeing the issue by myself, I started searching for the cause.
I opened three Explorer Windows, one with the local C: drive, one with the profile mapped homeshare and one with the commonly used data storage share drive.

The only window, which was closing occasionally, was the one with the common data storage, which lead me to the conclusion, that I should have a look at the GPOs.

Forcing a GPUPDATE reproduced the issue and I started searching on the net where I found this thread here.

The solution was exactly what user1084330 described.
Setting "Replace" to "Update" on the affected GPO solved the issue at the second GPUPDATE.