Hi Dimitris,
Thank you for contacting Intel.
I understand you have tried different driver versions to no avail. You may try to configure the adapter's advance settings.
Turn off or disable the following:
1. Performance options - Adaptive inter-frame spacing
2. Performance options - Interrupt moderation rate
3. ALL TCP/IP offloading options
See if there is improvement with your network connection. If no improvement, try below:
1. Increase the Transmit Descriptors buffer size.
2. Increase the Receive Descriptors buffer size.
Tuning Intel® Ethernet Adapter Throughput Performance
Hope this helps.
Sincerely,
Sandy