When the battery level drops below ~20% on a MacBook Pro or MacBook Air, macOS will decrease 10/25G Ethernet transmit performance in order to conserve battery life for the laptop.
The TWIN25G driver kit extension will not show in System Information>Software>Extensions.
To check whether the driver is installed, go to System Information>Hardware>Ethernet Cards. Click on one of the TWIN25G's ports and it should say Driver: com.sonnettech.sntmlx5e.
