I got the same problem as the OP. The problem is that "driveConnectorRuntime" gets lost with a level reload, but "_connectionData" does not (pesky static variables! ;), so driveConnectorRuntime will be null if you use e.g. Drive.GetAllTables() on Start() again, and that throws an error. Can you please make an update so it checks if driveConnectorRuntime is null or not?
(My hack right now is to make _connectionData public and setting it to null by hand in an OnDestroy().)