Proxmox Virtual Environment 6.1-3 / Debian 10 (buster)
Kernel 5.3.10-1-pve
Ethernet controller: Intel Corporation Ethernet Connection (2) I218-V (rev 05)
Ethernet driver: e1000e 3.2.6-k
Ethernet firmware: 0.1-4
The solution I've found was to create a oneshot service which disables segmentation offloading.
sudo apt update && apt -y install ethtool
Create the file /usr/lib/systemd/system/fix-e1000e.service with the following content:
[Unit]
Description="Fix for ethernet hang errors"
[Service]
Type=oneshot
ExecStart=/usr/sbin/ethtool -K NETWORK_INTERFACE tso off gso off
[Install]
After=network-online.target
Wants=network-online.target
systemctl daemon-reload
systemctl enable fix-e1000e
systemctl start fix-e1000e
/lib/systemd/system/fix-e1000e.service:10: Unknown key name 'Wants' in section 'Install', ignoring.
pve systemd[1]: /lib/systemd/system/fix-e1000e.service:9: Unknown key name 'After' in section 'Install', ignoring.