Probably some missing splash image, this is ugly as hell every time booting up.
yes its just one sec ! happens in some cases - nothing wrong - dont worry 
BTW: which board and OS installed ?
It’s VIM3, tried multiple Linux build, Ubuntu and Debian, all running from SD card. I don’t remember seeing this before I wiped out the original Android.
Yes, only exist with mainline uboot + mainline kernel.
I had the same issue, its only a bad outdated khadas image.
Even with that ksecure image you will be faced with resetting bootloader which killed my hole setup
Your best to find an update image