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.
This update corrupts the network settings. To recover, you need to delete the network plists and recreate your network settings.
Launch Terminal and type the following:
sudo rm /Library/Preferences/SystemConfiguration/NetworkPreferences.plist
sudo rm /Library/Preferences/SystemConfiguration/preferences.plist
Restart and recreate your network settings.
If that doesn't work, contact support@sonnettech.com. Be sure to save and send a System Report.