Question from mechdrew; Are you referring to the white screen that displays a the boot menu?
Which version(s) of DellEFI are you using on each Mini?
Not at the boot menu, just a white screen prior to the Dell startup screen and only for a couple of seconds and then it goes to the Dell startup screen. This is only on one of my Mini 9's. The other doesn't have a white screen; just starts up with a black screen and then goes to the Dell startup screen. Both machines have a 16gb SSD
and I used DellEFI 1.2a5 on both machines.
Thank you for your interest. BTW...your instructions for using a Mac and USB were very easy for me to follow, despite being technologically challenged.