Cubietruck freeze after 1-3 days with 5.23 Xenial (uboot problem?)

Hey,

after making sure that all packages are current (armbianmobitor upload available at http://sprunge.us/Migh)I still have the problem currently that my three cubietruicks freeze after working 1-3 days.

Mostly they are still ping-able, but no "heartbeat led blinking" happens anymore and SSH connect also not possible. The logs simply say nothing.

Is there anything knows with uboot 5.23 in case ob unstability?

The last uboot I remember that was quite stable was 5.20 ... Can I simply downgrade to that using

sudo apt-get install linux-u-boot-cubietruck-next=5.20

or such?

Thanks for an advice...

Ingo Fischer