server's host key did not match the signature provided

[Urbansh Xie]

Hi,I use OpenStack Ocata Dashboard to create instance,the the image are downloaded from openstack provided（https://docs.openstack.org/image-guide/obtain-images.html）.However,most Linux templates got error "server's host key did not match the signature provided" when I try ssh to the instance after created.I can login to the instance via console in dashboard.Also the set admin password feature not work on the dashboard interface if I switch to the old interface(The current doesn't have such option).I alreay set according to openstack guide:https://docs.openstack.org/nova/latest/admin/admin-password-injection.html.
I found some of the linux version don't have such problem,for saying Ubuntu 14.04 and CentOS 6.But Ubuntu 16 or 18、CentOS 7 or have such problem("server's host key did not match the signature provided").Openssh on Ubuntu 14.04 and CentOS 6 are openssh 5.X,and on Ubuntu 16 or 18、CentOS 7 are 7.X.I also try to downgrade openssh 7.X to 5.X but not still not work.
Is this related to Openstack policy setting?