If Mapped Network Drive keeps disconnecting on your Windows 10/8/7 system, then this post may help you in troubleshooting the issue. Here are a few options being suggested. Check to see what may apply to your version of the operating system or scenario.
Mapped Drive gets disconnected
1] Turn off the auto-disconnect feature
Windows will drop idle connections after a specified time-out period, I think it is 15 minutes by default, to prevent wasting resources. You can, however, easily re-establish the connection manually.
If you wish to turn off the auto-disconnect feature, type the following in an elevated command prompt and hit Enter.
net config server /autodisconnect:-1
2] Turn off auto-tuning network
If it occurs while copying large files over network drives, it could be due to the auto-tuning network.
To turn it off, open an elevated command prompt windows, type the following, and hit Enter:
netsh int tcp set global autotuninglevel=disabled
It should help.
3] Turn-off the auto-disconnect using Registry
To turn-off the auto-disconnect feature, you could also edit the Windows Registry. Navigate to the following key in the registry:
Change the hexadecimal value of autodisconnect to ffffffff. Click OK and Exit.
Hope something here helps you resolve the issue.
PS: More tips here if your Network drive keeps disconnecting.