After delete vpp nat cgnat, VPP's det44 tables are empty but det44-in2out / det44-out2in stay on the interfaces' ip4-unicast arc, so every routed packet is dropped as "No translation" until VPP is reconfigured. delete vpp nat nat44 does not have this problem.

Steps:

1. VPP on eth1 (inside, 10.51.3.9/24) and eth2 (outside, 10.51.4.9/24), a host on each side, routing works.
2. set vpp nat cgnat interface inside eth1, set vpp nat cgnat interface outside eth2, set vpp nat cgnat rule 100 inside-prefix 10.51.3.0/24, set vpp nat cgnat rule 100 outside-prefix 10.51.4.9/32, commit. Ping inside to outside: 20/20.
3. delete vpp nat cgnat, commit.
4. Ping again; check vppctl show errors and show interface features.

Actual (rolling, ~14 s after the commit; the same a minute later):

20 packets transmitted, 0 received, 100% packet loss, time 3946ms
## show det44 interfaces
DET44 interfaces:
## show errors (det44|nat44|translation)
        20            det44-out2in                      No translation             error
## show interface features eth1 (enabled arcs only)
ip4-unicast:   det44-in2out
ip4-unicast:   det44-in2out
## show interface features eth2 (enabled arcs only)
ip4-unicast:   det44-out2in
ip4-unicast:   det44-in2out

Cause: vpp_nat_cgnat.py only calls disable_det44_plugin() on removal, and VPP's det44 plugin (src/plugins/nat/det44/det44.c, same on VPP master) does not clean up: (1) det44_interface_add_del() passes enable=1 to vnet_feature_enable_disable() on delete; (2) det44_plugin_disable() passes the interface flags (1/2) as is_inside, so the outside interface is removed as inside (the extra det44-in2out on eth2); (3) it walks vec_dup() of the interface pool, freed entries included, and logs with unformat_vnet_sw_interface, which crashes VPP.

Suggested fix: disable the feature on delete, pass a boolean is_inside, walk the pool with pool_foreach, log with a format function. With the patched det44_plugin.so on rolling and stock vyos-1x, routing worked after the delete with no det44 feature left; rule changes and re-adding CGNAT still worked.