[OVS] Can't access instances on a compute and after restarted ovs-vswitchd it's back to normal

*Bug Description*

We are using openstack ussuri with openvswitch version 2.13.3 and ovn version 20.03.2.

We are using ubuntu 18.04.5 LTS with kernel 4.15.0-122-generic.

My question is sometimes and consistently all instances in one compute can't access and when hard reboot instance we got an error message: Unable to add port tapxxx to OVS bridge br-int.

After restart ovs-vswitchd service all instances can be accessed.