Proxmox network drivers are all quite unstable

we changed from normal libvirt kvm to proxmox...
before we had a good runing setup. never any problem.
now we just encounter one problem after another... started with problems of the windows ide drivers..
and now all our windows computer with rtl8139 lost all their network...
now changed to e1000 ... deactivating ipv6 freezes the machine... some windows clients also suddenly hang now without doing anything...
its catastrophic run a production cluster like this....