Why does commandTimeout raise SqlError in IDbConnection.Execute?

Question

I have an IDbConnection to a SQL server and two stored procedures I would like to start from a console app using the Execute method on the open connection. When I run the first one, there are no problems, but the second one takes more than 30 seconds to execute, so a Timeout is raised.

According to the Internet, waiting for a command to execute is changed with the commandTimeout parameter, but after adding the commandTimeout: 0, commandTimeout: 99999, or commandTimeout: null, both Executes raise a SQL error: String or binary data would be truncated.

These errors don't happen if I run the procedure in MS SQL Server Management Studio.

What should I do to wait for a longer time for the procedure to execute and why does adding a commandTimeout give and error about truncating? I tried searching for a solution, but I'm not well versed in C# yet and didn't find anything useful.

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Edit:

Some of you asked for tables or procedures, which I cannot give due to privacy reasons. However they are working correctly when executed in a query in the MS SQL Server Management Studio.

Here's the code in question:

public class MlCePredictedSqlSrvRepository : IMlCePredictedSqlSrvRepository
    {
        private IDbConnection _dbConnection;

        public MlCePredictedSqlSrvRepository(IDbConnection dbConnection)
        {
            _dbConnection = dbConnection;
        }

        public bool ExecuteStoredProcedure()
        {
            try
            {
                string sql = @"[dbo].[StoredProcedure]";

                _dbConnection.Open();
                var procedure = _dbConnection.Execute(sql, commandType: CommandType.StoredProcedure, commandTimeout: 0);
                _dbConnection.Close();

                Console.WriteLine("Stored Procedure successfully executed.");

                return true;
            }
            catch (Exception ex)
            {
                Console.WriteLine("\tException in the Stored Procedure: " + ex.GetType().Name + "; " + ex.GetBaseException().Message);
                _dbConnection.Close();
                return false;
            }
        }
    }

It's called directly in the Program. The only change from working (albeit with a Timeout) to not working is the last parameter in Execute