Dell C2665dnf problem

Hello,

I need some help with my printer. There are two issues:

1. Some time ago the network started malfunctioning - the printer couldn't get a DHCP IP address - checked my network, used different router etc. didn't help. Then checked the network configuration - all devices (including 2nd C2665dnf printer) worked fine, got IP, this one still didn't. I setup the IP manually - Web panel is available, but printing is once possible once not - printer is pingable, I can check status on the web portal, but none of PCs/Mac can print, just "looking for printer". Airprint function at this point is not findable. Multiple restarts fixed the issue for a while and then, somtimes after an hours, sometimes the next day - it starts all over again. 

I looked through the net for some answers and found threads like
https://www.dell.com/community/Printers/C2665dnf-won-t-print-via-network-all-the-sudden/td-p/6102042
No help there.

Firmware upgrade did not help - DHCP still not working, net functions once work, once not.
Next step: I restored factory defaults (all possible restores / inits in CE mode) - did not help. 
I tried, and that may have been my bad, removing the 3V battery on the MB - left the printer for 5 minutes like that, placed the battery back and turned it on. This is where the 2nd issue started

2. After the printer was turned on I got 116-364, like described here: https://www.dell.com/community/Printers/please-help-I-have-my-DELL-c2665dnf-showing-up-116-364-error/td-p/7403877

What I tired to do - again restored everything - did not help, accessing the printer through the web panel (tricky part as by default AutoIP sets the address) and setup the clock - did not help. I made the printer to sync with NTP server - did not help. Still facing the 116-364, although the clock shows correct time and printer cannot be started.

When I tried to get support on Dell page, I needed to place the service tag - but I faced another issue with it - It's not found (like someone described here: https://www.dell.com/community/Rack-Servers/Service-Tag-Not-Found/td-p/7416733) 

Long story short:
I need to get rid of 116-364 and then fix the network issues. That's one option, the other is: Instead of wasting time for bug hunting or configuration issues I found that a new mother board in US costs around $20 (available on Walmart and Amazon) - I wanted to buy it but they don't send to Europe. I googled and did not find it anywhere on Europe's net.

Anyone any ideas how to fix my issues OR where in Europe to get a new MB ? 

Thanks in advance,

Best Regards
Tom