Symptoms
After establishing VPN connection to the APS2 sandbox on Mac OS using Tunnelblick you can access hosts via IP addresses but DNS is unstable, sometimes it works, but mostly it does not.
Cause
Certain versions of Tunnelblick can cause such DNS issues.
Resolution
We have a recommended version of Tunnelblick that does not have this issue with some installation instructions available here.
You can also try alternative VPN clients for Mac OS, like Viscosity.