Sometime client, test you and your patience.
They may like to know how you react if they delay, how you respond to their queries. This test help them to decide if he can think to work with you in future or not. Your way of handling response of client will help him to recommend about you to others.
You can take this as positive side.
One solution to execute project in perfect way is to, write each and points related with project in proposals make client understand.
Also think client have many work to do, do he may not be able to give time to reply you, in that case just have patience.
Just do your part in perfect way and give extra value addition to client.