Slow ethernet after sleep

[AntarcticPL]

Been struggling with this for a while ... I'll describe the issue

Hardware: Gigabyte Aorus X570 Master with Realtek® 2.5GbE + Intel® Gigabit LAN
Using LucyRTL8125Ethernet.kext in Opencore 0.8.4
Using new 2,5 Gb cable
In System Preferences, the Ethernet Automatic setting selects speed at 1000baseT.

• After a fresh restart of my computer the Ethernet works at full speed. Transferring files to my Synology NAS at gigabit speed (internal network at home is 1 Gbps).
• After a computer sleep mode, the Ethernet wakes a bit slow, but worse, the speed is crippled and I cannot transfer large files to my NAS without errors --> files are erroneous

Anyone recognizes this? Am I using the wrong kext with the Mobo or ethernet chipset? Should I use a 1 Gb cable?

thanks for supporting!