fuel 6.1 delete node fail (Can't unassign nodes with ids <nailgun.db.sqlalchemy.models.node.Node object at 0x4d93a10> if they not assigned.)

[root@fuel ~]# fuel node
DEPRECATION WARNING: /etc/fuel/client/config.yaml exists and will be used as the source for settings. This behavior is deprecated. Please specify the path to your custom settings file in the FUELCLIENT_CUSTOM_SETTINGS environment variable.
id | status | name | cluster | ip | mac | roles | pending_roles | online | group_id
---|--------|-------|---------|--------------|-------------------|---------------------------|---------------|--------|---------
1 | ready | UCS1 | 1 | 168.5.21.100 | 00:25:b5:00:00:11 | cinder, controller, mongo | | True | 1
2 | ready | UCS2 | 1 | 168.5.21.101 | 00:25:b5:00:00:21 | cinder, controller, mongo | | True | 1
3 | ready | R420 | 1 | 168.5.21.102 | 00:1b:78:5a:9e:46 | cinder, controller, mongo | | True | 1
4 | ready | R720 | 1 | 168.5.21.103 | c8:1f:66:d0:33:83 | compute | | True | 1
7 | error | RD530 | 1 | 168.5.21.104 | f8:0f:41:f7:2a:bc | compute | | True | 1
[root@fuel ~]#
[root@fuel ~]#
[root@fuel ~]# fuel env
DEPRECATION WARNING: /etc/fuel/client/config.yaml exists and will be used as the source for settings. This behavior is deprecated. Please specify the path to your custom settings file in the FUELCLIENT_CUSTOM_SETTINGS environment variable.
id | status | name | mode | release_id | pending_release_id
---|--------|--------------|------------|------------|-------------------
1 | error | evecom-cloud | ha_compact | 1 | None
[root@fuel ~]#
[root@fuel ~]#
[root@fuel ~]#
[root@fuel ~]# fuel node remove --node-id 7 --env-id 1
DEPRECATION WARNING: /etc/fuel/client/config.yaml exists and will be used as the source for settings. This behavior is deprecated. Please specify the path to your custom settings file in the FUELCLIENT_CUSTOM_SETTINGS environment variable.
400 Client Error: Bad Request (Can't unassign nodes with ids <nailgun.db.sqlalchemy.models.node.Node object at 0x4d93a10> if they not assigned.)

I cannot remove node which status is error, why?
If I use 'fuel node --node-id <id> --delete-from-db', it can work, but when i redeploy this machine(R530), it always failed, and then node status turns to error. I think there must be something wrong with my fuel database.
Anyone can help me?