u-boot USB RPi Zero - unable to get device descriptor

[diffusae]

Hello,

I've recognized a problem with u-boot and USB devices at RPi Zero.

If I power up the device, it looks like this:

starting USB...
USB0:   Core Release: 2.80a
scanning bus 0 for devices... 3 USB Device(s) found
       scanning usb for storage devices... 0 Storage Device(s) found
       scanning usb for ethernet devices... 0 Ethernet Device(s) found
Booting from: mmc 0 ubldr.bin

Everything is working correct and a USB LAN adapter is detected.

If I reboot the device not all USB devices are recognized and I get an
error from u-boot ("unable to get device descriptor"):

scanning bus 0 for devices... unable to get device descriptor (error=-22)
2 USB Device(s) found
       scanning usb for storage devices... 0 Storage Device(s) found
       scanning usb for ethernet devices... 0 Ethernet Device(s) found
Booting from: mmc 0 ubldr.bin
reading ubldr.bin
224136 bytes read in 31 ms (6.9 MiB/s)

Only the USB Hub is detected, the USB LAN adapter stops working.
Is this related to u-boot? Could it be due to "faulty" USB device?

I guess, I need some help, to get this working.

Regards,