Package: network-manager Version: 1.28.0-2+b1 NetworkManager runs the ifupdown scripts on certain events, but especially /etc/network/if-post-down.d/ifenslave interferes with bond setup somehow.
See
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/660
for the investigation. NM upstream says:
That's bad. The script shouldn't to that. Please report it to debian
or ifenslave package.
So here you go. :)
