Slow sending orders to RapidCart Pro

I use a store built on RapidCart Pro 4, the whole deal works fast and there is no slowdown. Once you get to the end and send the order, the order is sent very long time - 3 minutes. Another flaw is that after sending will not be redirected to a thank you page. Developers RapidCart not know what the problem is and hosting trade area located where I too have not been able to say what the problem is. Does anyone know what could cause this problem?