K8s freezes with net.ipv4.ip_forward allowed

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1 
sudo /usr/local/bin/k3s \
    server \
        --kubelet-arg=allowed-unsafe-sysctls=net.core.rmem_max,net.core.wmem_max,net.ipv4.ip_forward \
        --flannel-backend none \
        --disable=traefik \

k3s freezes when i added net.ipv4.ip_forward to allow-unsafe-sysctls, how do i fix this? or how do i debug this