Comment # 3 on bug 1002194 from Freek de Kruijf

(In reply to Andreas F�rber from comment #2)
> If it is rather in U-Boot (before GRUB starts) you can try a newer
> u-boot-rpi3 from Base:System:Staging project. (Just download and extract the
> .rpm, e.g., in File Roller to get the u-boot.bin and put it onto the FAT
> partition.)

Yes, it is.
> 
> There's also an update to raspberrypi-firmware that just got accepted into
> Factory today.
> 
> When using USB disks on the Pis always make sure they are externally powered.

Will report back when tried.