Commit

3394dd7

Check if your servier is has mptcp
sysctl net.mptcp.enabled
Check if your server is using mptcp
sudo ss -Mlnp
If you are not using it, then just disable it ...
bash
echo 'net.mptcp.enabled = 0' | sudo tee /etc/sysctl.d/90-disable-mptcp.conf
sudo sysctl -w net.mptcp.enabled=0

commit 3394dd7