Hi, 
  
I will take a guess that the issue is when you are viewing them with IVMS, 
I have had a long history with this software, when dealing with 96 2MP  
cameras the software seems to suffer. 
The telling sign, when there is a delay on IVMS, use a web browser to log 
into the same camera and the time stamp will be different. 
Give me more info on your setup and maybe i can suggest a few tweaks. 
  
Regards