Ethernet cable unplugged only when restarting from Ubuntu 20.04 LTS to Windows 10

I have a desktop computer with the good old Asus Sabertooth x58 motherboard. My setup is a dual boot with Ubuntu 20.04 LTS and Windows 10.

Since some month ago, I noticed that my ethernet works fine, except when I decide to restart from Ubuntu and choose Windows. In that situation, Windows says my ethernet cable is unplugged, even if I restart to Windows more times. The only way to solve that is to shut down the computer and the power supply for 5-10 seconds, and then it works fine.

Restarting from Windows to Windows/Ubuntu and from Ubuntu to Ubuntu works as expected (from Windows to Windows only if Ethernet works well, otherwise, the problem persists).

I have a weirder problem when I had Ubuntu 18.04 LTS, because it didn't allowed me to have 1000 MB/s Full Duplex, but it solved automagically when I installed the next LTS. I tried yesterday to reinstall my Windows 10, hoping to have another automagical fix, but the problem persists.

I suspect there may be a malfunction on the Ethernet card, because I didn't have any problem like this a year ago, but I'm still willing to find a way to solve it before buying a new card.

Edit In Ubuntu, ethtool -S enp7s1 returns

NIC statistics:
     tx_packets: 43876499
     rx_packets: 56660374
     tx_errors: 0
     rx_errors: 0
     rx_missed: 11418
     align_errors: 0
     tx_single_collisions: 0
     tx_multi_collisions: 0
     unicast: 56592808
     broadcast: 36223
     multicast: 31344
     tx_aborted: 0
     tx_underrun: 0

and ethtool enp7s1 returns

Settings for enp7s1:
        Supported ports: [ TP MII ]
        Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/Half 1000baseT/Full 
        Supported pause frame use: Symmetric Receive-only
        Supports auto-negotiation: Yes
        Supported FEC modes: Not reported
        Advertised link modes:  10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/Half 1000baseT/Full 
        Advertised pause frame use: Symmetric Receive-only
        Advertised auto-negotiation: Yes
        Advertised FEC modes: Not reported
        Link partner advertised link modes:  10baseT/Half 10baseT/Full 
                                             100baseT/Half 100baseT/Full 
                                             1000baseT/Full 
        Link partner advertised pause frame use: No
        Link partner advertised auto-negotiation: Yes
        Link partner advertised FEC modes: Not reported
        Speed: 1000Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 0
        Transceiver: internal
        Auto-negotiation: on
        Supports Wake-on: pumbg
        Wake-on: d
        Current message level: 0x00000033 (51)
                               drv probe ifdown ifup
        Link detected: yes