Clonezilla imaging identical macbooks, different boot times

I'm using clonezilla to image a few macbooks with identical specs. However, only the macbook with the original installation from which the image is created boots normally. The other macbooks that I image with clonezilla boot up with 10 seconds of grey screen before the apple logo appears. The macbook wiith the original install boots directly to the apple logo, no pause after power on.

What goes on here? If the hardware is the same, why do the imaged machines hang on boot? Thanks in advance.

 

keysofanxiety PRAM reset solved it. Funny, because i had already PRAM reset each of these macbooks in order to by-pass the admin password that was stopping me from using clonezilla. So doing it once again was not a problem. It seems PRAM reset is a more versatile tool than I had thought. Thanks for showing me something new..