I know it's been a long time since post , but i 've been frustrated with an answer because i had the same problem and thought that someone who has the same problem like me could try my solution.
After 1.16 , if you have SMTP disabled (mine was not working because the hosting provider was blocking gmail authentication) any reply with take you to a blank page.The posted reply though will be registered in osticket.
If you choose to not email reply to recipients,the post is completed without redirecting you to a blank page.
So , make sure you have SMTP enabled