@Crypto2Alt

thx for the hints. I logged into it by ssh and i'am pretty sure now that its indeed connected to the /etc/network file .

When i tried to edit the /etc/network i got the following in SSH
"Error reading lock file /etc/network.interfaces.swp:Not enough data read"

I was afraid of changing anything at this moment as i have only basic ssh skills and did not want to mess anything totally up. You know, at least the baikal works
right now until the next failure.

But, i'am pretty sure now that these failures are indeed related to this /etc/network thingie.
Why?
- New orange pi got the same mistake, but after restarting the baikal, cleaning all cashes and cookies and a reset it went back to work while i allready was sure
that the next orange pi is vaulty now. This is not the case, the orange pi is in full working order.
- Earlier today in the morning, the internet stopped for some seconds and you guess it, exactly this Baikal stopped working again. Pretty sure it is due this
missing or vaulty /ect/network data file. Just by the way, this internet disruption brought my L3's as well out of working order and 1 of them did not restart too.
While the S9's, the other Baikals and the D3's had not problem with the internet disruptin. Just in case it is of interest for someone.

This said, i'am pretty sure now that the problem is indeed like here discussed the /etc/network/ file(s).

My question now is:
- how do i handle this /etc/network/ data read file (explained about what error i get)
- how can i replace this file for example from another working Baikal? SSH? How?
- Can i write the suggested changes and save it to a file like suggested even with the error i got while opening the file? If yes, as what do i have to save it?
- Any other advices and tips?

Forgot to write. The Baikal is working perfectly right now for at least 12 hours again and the web login is working as well, but i'am pretty sure that at the next short internet interuption it will fail again.