There is another thread about Marvell 10Gb LAN. Not quite the same problem, but take a look. https://rog.asus.com/forum/showthread.php?128211-Z690-Formula-Constant-loss-of-ethernet-on-load/page...
It might help. The best general advice there seemed to be:
1. Use Marvell Ethernet connection Driver V188.8.131.52 from our support site to see if the slowing down and disconnecting issue still occurs.
2. Disable "Recv Segment Coalescing (IPv4) and (IPv6 if needed)" in LAN adapter properties
3. If there are options like Energy-Efficient Ethernet, Power Saving Mode in device manager > network adapters(Marvell) > properties > advanced, please disable them to see if the issue persists.
I can't help you directly, sorry, I don't have 10Gb LAN myself, but just making you aware of that thread if you haven't seen it yet. Bon chance!
Z690 Hero, BIOS 2305, ME Firmware 184.108.40.2066, 7000X Case, RM1000x PSU, i9 12900K, ASUS TUF OC 3090TI, 2 x 16GB Corsair RAM @ 5200MHz, Windows 11 Pro 22H2, Corsair H150i Elite AIO, 4x Corsair RGB fans, 3x M.2 NVME drives, 2x SATA SSDs, 2x SATA HDs.