The fix was to add the internal IP address of the nas 192.168.248.15 to the lab DNS. Now

PS C:\Users\gquest> ping nxc.mccullerlab.com

Pinging nxc.mccullerlab.com [192.168.248.15] with 32 bytes of data:
Reply from 192.168.248.15: bytes=32 time<1ms TTL=64
Reply from 192.168.248.15: bytes=32 time<1ms TTL=64
Reply from 192.168.248.15: bytes=32 time<1ms TTL=64

Also added 

nas.lab, docs.mccullerlab.com, files.mccullerlab.com to this IP address.