Strange SQL performance issue using Dapper & Oracle

I'm having a great time with Dapper and having no real issues up to this one, and it's driving me mad.

Given this call to an Oracle method inside a package

begin
  package.method(in_table => :in_table,
                 in_clob_type => :in_clob_type,
                 out_error_table => :out_error_table);
end;

• From within PL/SQL developer or any other Oracle tool it takes approx. 2 seconds to run.
• From within a standard C# console test app it takes approx. 2-3 seconds.
• From within an IIS hosted WebAPI app it takes approx. 10-12 seconds.

Same SQL, same parameters, same database and same user. Every other piece of SQL within the application works perfectly

var errorTable = string.Empty;
var parameters = new DynamicParameters();

parameters.Add("in_table", "table-name");
parameters.Add("in_clob_type", 0);
parameters.Add("out_error_table", dbType: DbType.String, size: 32, direction: ParameterDirection.Output);

db.Query("package.nethod", parameters, commandType: CommandType.StoredProcedure);

// Query or Execute makes no difference
// db.Execute"package.nethod", parameters, commandType: CommandType.StoredProcedure);

errorTable = parameters.Get<string>("out_error_table");

Any one have any ideas on the best way to debug this?

UPDATE 1:

Both WebAPI and the console code produce 1708 distinct SQL statements for insertion and update processes within the package function. It just takes a longer between SQL calls but I can't see a pattern as yet.

UPDATE 2:

Digging deeper, not my code so it's taking a little longer, found a call that creates some temp tables into which we load the data required for the process. If I comment this out and just provide an existing table name, 2-3 seconds.

Something in the creation of the tables seems to be blocking the rest of the process? If I mark all the methods PRAGMA AUTONOMOUS_TRANSACTION 10-12 seconds. If I create tables in or out of a specific or shared transaction, 10-12 seconds. If I create them without a transaction 10-12 seconds.