Hello,
I also had similar problem, then I used reference_id in place of carrier_id. So now even when changing the carrier options it displays my carriers at check out and all works well.
But now my problem is that, the speed slows down after I change the delay of any carrier.
I think changing carrier options should not affect the speed.
Is it some thing that should be taken care of, and is left by my side or unknown to me.
Please guide me through this.
Thank You