Rock3a falls unresponsive with blue LED blinking and no Network until hard reboot

Question:
Did anyone experience the same behavior?
And if so, what can be done about?
I’m using a most recent rock3a (November 2021 delivery) with RADXA Ubuntu 20.04 with 3 HDDs (sda is a SSD) mounted and running on the - unfortunately still nonfunctional PENTA SATA HAT -
Once in a while 6 to 8 Hours after boot the whole thing (NO OVERHEATING detected yet) falls unresponsive to any external command with blue Led constantly blinking.
I need to reboot via Power Off and it takes about 5 Minutes for it , to return to life after this.
After a normal reboot the thing is back online within less then 30 seconds.
Curretly I’m booting from SD CARD

Could be lots of things:

  • Out of Memory crash? (swap set-up?)
  • Hibernation set-up?

Any information in the logs? (/var/log)

Could be lots of things:
Out of Memory crash? (swap set-up?) NO! just SAMBA and NFS running
Hibernation set-up? Random Hybernation ??"

Any information in the logs? (/var/log) That may take some time to analyze not really knowing what to look for!