Dapper giving unhandled exception when trying to insert data to database

Question

I'm writing a C# plugin for Autodesk Navisworks that will iterate through a bunch of 3D elements and write their properties (Category and Family of the element for now) into an Azure database.

I'm using Dapper as ORM. When I try to insert the data in the database Navisworks crashes giving an unhadled exception.

I tried the ssame procedure with plain sql and everything works fine so I'm quite sure it's Dapper's Execute function giving the exception.

This is my object:

    internal class NavisTest
    {
        public string Category { get; set; }
        public string Family { get; set; }

        public NavisTest(string category, string family)
        {
            Category = category;
            Family = family;
        }
    }

This is the sql command:

const string navisTestSql = "insert into NavisTest " +
            "(Category, Family) " +
            "values (@category, @family);";

And this is the main logic:

using (SqlConnection connection = new SqlConnection(
        NavisDbSettings.ConnectToDB().ConnectionString))
{
    // Open connection to db
    connection.Open();

    using (SqlTransaction transaction = connection.BeginTransaction())
    {
        NavisTest navisTest = new NavisTest(
            "Wall",
            "Concrete Wall 01");

        connection.Execute(NavisDbSqlCommands.navisTestSql, navisTest, transaction: transaction);

        // Commit database transaction
        transaction.Commit();
    }
}

So when this runs Navisworks just crashes, but if I do with a normal SqlCommand everything works fine. (Also I basically copied the code to insert to the db from another application I have that works perfectly)

Also, if I try to surround the code in a try-catch clause, it still fails (it's an unhandled exception).

I really don't understand what I'm doing wrong.

Any ideas?