while using QueryFirstOrDefaultAsync without Using block ,getting wrong result in output

While using QueryFirstOrDefaultAsync ,In a certain scenario where the outbound connection in Azure appservice is high , output of the query gives wrong result

Code Sample : var orderDetail = await connection.QueryFirstOrDefaultAsync(query).ConfigureAwait(true);

We are able to fix the issue after wrapping the code(connecting object) inside using block

using (var connection = new SqlConnection(FiddleHelper.GetConnectionStringSqlServerW3Schools()))
{
var orderDetail = await connection.QueryFirstOrDefaultAsync(query).ConfigureAwait(true);
}

Not sure, how disposal of connection object helped to resolve the issue
Can any one help me to find the theory behind it?

Start by examining the connection lifetime around SqlConnection and QueryFirstOrDefaultAsync in the Azure App Service scenario. Reproduce the reported wrong result with and without the using block, recording the query and connection conditions described in the issue. Done means establishing a minimal reproducible case and clearly documenting the cause or required connection-lifetime behavior.