Proxmox Intel NIC e1000e hardware unit hang

Make sure ethtool is installed.

Check what offload technology is enabled for the network card and the bridge, for example:

ethtool -k eno1 | grep offload
ethtool -k vmbr0 | grep offload

Manually disable what you need for both and test:

ethtool -K eno1 gso off gro off tso off rx-vlan-offload off tx-vlan-offload off

ethtool -K vmbr0 gso off gro off tso off tx-vlan-offload off

To disable hardware offload, edit /etc/network/interfaces:

iface eno1 inet manual
        post-up ethtool -K eno1 gso off gro off tso off rx-vlan-offload off tx-vlan-offload off

auto vmbr0
iface vmbr0 inet static
        address 172.XX.XX.XX/24
        ...
        post-up ethtool -K vmbr0 gso off gro off tso off tx-vlan-offload off