Hi Sourabh,
it doesn't look usual to me. When you say that you have just finished SPL refresh, do you mean that you have done delta SPL load? It would be worth checking if there is a SPL with blank Name and/or address. Else kindly check if there is a pattern in those blocked Sales Order I.e. One particular country or business partner etc.
You can start with checking screening log of few of them.
regards,
Kul Vaibhav