It may be that the bridge was not correct. If the strings sit too deep in the grooves in the bridge, the A and D are almost impossible to find. Played one yesterday that this was the case. I could not find my double stops at all. Have your violinist friend check the bridge, and if the strings are not all even about 1/16th of an inch in front of the bridge, the bridge will need to be re cut. Take to a shop to have this done, bridge cutting and setting is an art unto itsself.